@glasfaser
DANKE!!!
Auch an alle anderen, die mir die ganze Zeit über mit Rat und Tat geholfen haben. Ich vermute, dass sich tatsächlich ein Problem auf der Synology eingeschlichen hatte (vielleicht beim Update auf die DSM 6.2.4?!)
-> Lösung: Synology Backup durchgeführt -> Synology zurückgesetzt -> DSM neu installiert -> Benutzer und Ordner neu eingerichtet -> Berechtigungen geprüft -> funktioniert 
Hier noch die finalen Logs. 1) ioBroker und 2) Homematic-CCU
Started iobroker ...
[DEBUG] [mount] start with {"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"backups/iobroker","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****"}
[DEBUG] [mount] - noserverino option: false
[DEBUG] [mount] - cifs-mount command: "sudo mount -t cifs -o username=backupuser,password=****,rw,file_mode=0777,dir_mode=0777,vers=3.0 //192.168.178.56/backups/iobroker /opt/iobroker/backups"
[DEBUG] [mount] - mount successfully completed
[DEBUG] [mount] - done
[DEBUG] [iobroker] start with {"type":"creator","time":"02:40","debugging":true,"slaveBackup":"Single","everyXDays":"1","deleteBackupAfter":0,"cifs":{"enabled":true,"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/iobroker","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","context":{"fileNames":[],"errors":{},"done":["mount"],"types":[]},"adapter":null,"influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[]},"dir":"/opt/iobroker","historyHTML":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"historyJSON":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"backupDir":"/opt/iobroker/backups"}
[DEBUG] [iobroker] - host.raspberrypi4-iob 2643 states saved
[DEBUG] [iobroker] - host.raspberrypi4-iob 2777 objects saved
[DEBUG] [iobroker] - Backup created: /opt/iobroker/backups/iobroker_2022_01_01-21_35_15_backupiobroker.tar.gz
[DEBUG] [iobroker] - done
[DEBUG] [cifs] - done
[DEBUG] [cifs] start with {"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/iobroker","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","backupDir":"/opt/iobroker/backups","influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[],"deleteBackupAfter":0}
[DEBUG] [clean] - done
[DEBUG] [historyHTML] - new history html values created
[DEBUG] [historyHTML] - done
[DEBUG] [historyJSON] - new history json values created
[DEBUG] [historyJSON] - done
[DEBUG] [historyHTML] start with {"type":"creator","time":"02:40","debugging":true,"slaveBackup":"Single","everyXDays":"1","deleteBackupAfter":0,"cifs":{"enabled":true,"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/iobroker","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","context":{"fileNames":["/opt/iobroker/backups/iobroker_2022_01_01-21_35_15_backupiobroker.tar.gz"],"errors":{},"done":["mount","iobroker"],"types":["iobroker"]},"adapter":null,"influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[]},"dir":"/opt/iobroker","historyHTML":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de","time":"01. Januar 2022 um 21:35 Uhr"},"historyJSON":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"backupDir":"/opt/iobroker/backups","influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[]}
[DEBUG] [umount] - mount activ, umount is started ...
[DEBUG] [historyJSON] start with {"type":"creator","time":"02:40","debugging":true,"slaveBackup":"Single","everyXDays":"1","deleteBackupAfter":0,"cifs":{"enabled":true,"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/iobroker","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","context":{"fileNames":["/opt/iobroker/backups/iobroker_2022_01_01-21_35_15_backupiobroker.tar.gz"],"errors":{},"done":["mount","iobroker"],"types":["iobroker"]},"adapter":null,"influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[]},"dir":"/opt/iobroker","historyHTML":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"historyJSON":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de","time":"01. Januar 2022 um 21:35 Uhr"},"backupDir":"/opt/iobroker/backups","influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[]}
[DEBUG] [umount] start with {"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/iobroker","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","backupDir":"/opt/iobroker/backups","influxDBEvents":[],"mySqlEvents":[],"pgSqlEvents":[]}
[DEBUG] [umount] - umount successfully completed
[DEBUG] [umount] - done
[EXIT] 0
Started ccu ...
[DEBUG] [mount] start with {"mountType":"CIFS","type":"storage","source":"cifs","mount":"192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"backups/ccu","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****"}
[DEBUG] [mount] - noserverino option: false
[DEBUG] [mount] - cifs-mount command: "sudo mount -t cifs -o username=backupuser,password=****,rw,file_mode=0777,dir_mode=0777,vers=3.0 //192.168.178.56/backups/ccu /opt/iobroker/backups"
[DEBUG] [mount] - mount successfully completed
[DEBUG] [mount] - done
[DEBUG] [ccu] - CCU-Backup started ...
[DEBUG] [ccu] start with {"type":"creator","time":"01:30","debugging":true,"everyXDays":"3","deleteBackupAfter":0,"signedCertificates":true,"cifs":{"enabled":true,"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/ccu","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","context":{"fileNames":[],"errors":{},"done":["mount"],"types":[]},"adapter":null,"ccuEvents":[]},"historyHTML":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"historyJSON":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"host":"192.168.178.61","user":"Admin","usehttps":false,"pass":"****","ccuEvents":[],"ccuMulti":false,"backupDir":"/opt/iobroker/backups"}
[DEBUG] [ccu] - CCU Version: 3.61.6
[DEBUG] [ccu] - Requesting backup from CCU
[DEBUG] [ccu] - CCU-Backup for is finish
[DEBUG] [ccu] - done
[DEBUG] [cifs] - done
[DEBUG] [cifs] start with {"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/ccu","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","backupDir":"/opt/iobroker/backups","ccuEvents":[],"deleteBackupAfter":0}
[DEBUG] [clean] - done
[DEBUG] [historyHTML] - new history html values created
[DEBUG] [historyHTML] - done
[DEBUG] [historyJSON] - new history json values created
[DEBUG] [historyJSON] - done
[DEBUG] [historyHTML] start with {"type":"creator","time":"01:30","debugging":true,"everyXDays":"3","deleteBackupAfter":0,"signedCertificates":true,"cifs":{"enabled":true,"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/ccu","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","context":{"fileNames":["/opt/iobroker/backups/homematic_2022_01_01-21_41_13_3.61.6_backupiobroker.tar.sbk"],"errors":{},"done":["mount","ccu"],"types":["homematic"]},"adapter":null,"ccuEvents":[]},"historyHTML":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de","time":"01. Januar 2022 um 21:41 Uhr"},"historyJSON":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"host":"192.168.178.61","user":"Admin","usehttps":false,"pass":"****","ccuEvents":[],"ccuMulti":false,"backupDir":"/opt/iobroker/backups"}
[DEBUG] [umount] - mount activ, umount is started ...
[DEBUG] [historyJSON] start with {"type":"creator","time":"01:30","debugging":true,"everyXDays":"3","deleteBackupAfter":0,"signedCertificates":true,"cifs":{"enabled":true,"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/ccu","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","context":{"fileNames":["/opt/iobroker/backups/homematic_2022_01_01-21_41_13_3.61.6_backupiobroker.tar.sbk"],"errors":{},"done":["mount","ccu"],"types":["homematic"]},"adapter":null,"ccuEvents":[]},"historyHTML":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de"},"historyJSON":{"enabled":true,"type":"message","entriesNumber":"25","systemLang":"de","time":"01. Januar 2022 um 21:41 Uhr"},"host":"192.168.178.61","user":"Admin","usehttps":false,"pass":"****","ccuEvents":[],"ccuMulti":false,"backupDir":"/opt/iobroker/backups"}
[DEBUG] [umount] start with {"mountType":"CIFS","type":"storage","source":"cifs","mount":"//192.168.178.56","debugging":true,"fileDir":"/opt/iobroker/node_modules/iobroker.backitup","wakeOnLAN":false,"macAd":"20:DE:20:DE:20:DE","wolTime":"25","smb":"vers=3.0","sudo":true,"cifsDomain":"","clientInodes":false,"deleteOldBackup":true,"ownDir":true,"dir":"/backups/ccu","dirMinimal":"backups/iobroker","user":"backupuser","pass":"****","backupDir":"/opt/iobroker/backups","ccuEvents":[]}
[DEBUG] [umount] - umount successfully completed
[DEBUG] [umount] - done
[EXIT] 0
