First of all many thanks for your help and commitment
- Unfortunately I don't have a test instance so I could test this.
- Neither paths, files nor file date were changed.
- Nothing has been changed in the settings of the forum and everything is the same as it always worked except that Plesk has been updated to 23.
- Databases are completely backed up daily, even with incremental backups, there are no changes here that might interfere (about 400 MB daily).
- I've looked at the incremental backup of today and the size clearly comes from files (pictures for the most part) that are on the webhosting but which are older and have already been backed up in the full backup, so that they should not be backed up in the incremental backup.
I also checked and saw that the other webhostings are also affected by the problem, but there it is not so obvious because less storage space is needed and there all backups are valid, so I can rule out the valid one.
The only thing I did after updating Plesk yesterday was to delete the custom templates and replace with the current defaults and remove the powered by PleskLin and regenerate the confs. Don't think that this is related to the backup feature and will lead to this behavior.
This has to be observed tomorrow, if everything is still running then, there was somehow a problem or hiccup ☺️