Can not Change Quota for some User

i use IONOS Managed Nextcloud installation.
I tried to change the Quota of my Users. Some succed but some not possible.
They have right now 1 TB i want to change to 10 GB. I can type select and then see the Change.
But after i go on a other page and come back to User configuration it is still 1 TB.
What additional Information you need to support me? Is it a known issue?
Thank you

After you make the change are you clicking the check mark icon to the far right?

Otherwise, what version of Nextcloud Server?

Did you ever find a solution to this issue? It is a problem on my 29.0.3 installation. I cannot change a user from 10GB to unlimited. It seems that at least the web interface does nothing. I may be faced with deleting a user and recreating the user with the new quota.