Pop-ups freezing & non-clickable since version 1.5.1

If it is exactly the upgrade from 1.5.0 to 1.5.1 that introduced the error, it might be caused by switching to JDK 14. We also have another user report of an erronous GUI since an upgrade from 1.5.0:

It is a different error, but it is also in the GUI and it appears on a system with a linux kernel.

We’ll look into this problem.