Ik denk niet dat het de permissions zijn. Alles staat goed hier lijkt me, zie screenshot. De account Jerome kan ik niet verwijderen, de account admin heb ik net zelf toegevoegd.
Wel onderstaand tegengekomen:
Associate a New Drive with an Existing Time Machine Backup
Apple configured Time Machine to identify source drives with a unique identifier (UUID), something that is assigned when the drive is formatted and a new file system is created. Time Machine won’t incrementally back up a new drive to an existing set of snapshots; it will instead create a separate backup point when enabled and backup everything anew. This usually works fine, and helps prevent critical Time Machine data from getting mixed up between drives if you connect your external Time Machine drive to another computer, for example.
But what if your Mac’s system drive is starting to fail and you clone the data to a new drive? Or what if you’ve just restored a new Mac from a Time Machine backup? In both cases, most users would want to continue to use the existing Time Machine backup instead of starting from scratch but, because any new or reformatted drive has a different UUID, Time Machine won’t recognize it.
To solve this problem, you can manually associate a Time Machine backup with a new drive using the “associatedisk” command. To start, browse to your Time Machine backup drive and find the latest snapshot, which should be located at /Volumes/[Time Machine Drive]/Backups.backupdb/[System Name]/Latest/[Drive].
Next, open Terminal, type the following command, and press Return. Use the path above for “Snapshot Volume” and the path of your new or newly formatted drive as “Source:”
sudo tmutil associatedisk [-a] “[Source]” “[Snapshot Volume]”
In our iMac example, the command is:
sudo tmutil associatedisk [-a] “/Volumes/System” “/Volumes/Time Machine/Backups.backupdb/iMac/System”
You’ll need to enter your admin password but, after doing so, you’ll find that Time Machine now treats your new drive exactly the same as your old drive, and your backups will be incremental instead of complete backups from scratch. This can save both time and allow you to access and restore older data.
source:
https://www.techjunkie.com/become-time-machine-power-user-terminal-commands/Klinkt aannemelijk...?