Failed to write to project library folder (MacOS)

Hi all,

I'm working on a Mac. I have 2 Project Database on my local disk to separate Client Projects from my Own Projects. Since 13.apr. I haven't opened my Own Projects database (now is 10.mai.), but last time it was working.

Now I'm trying to switch to Own Projects I get the Warning Popup:
Failed to write to project library folder
'/Users/MyUser/DaVinciProjectLibraries/OwnProjects'
Please make sure you have correct permissions.

Then I created a Diagnostic Log. In it I found the following:
mkdir failed for directory '/Users/MyUser/DaVinciProjectLibraries/OwnProjects/Resolve Projects/Users//ProjectMetadataCache/' (errno 1)

The folder Users is RW enabled for everyone
I found a Users/guest/ProjectMetadataCache/ folder, it's pretty new.
The drive has 900GB free space.

What can be the problem? How can I solve it?

Thanks!