Thank you for your answer Paul,
my solution at the moment is not to use the SPPB editor, but to switch to the system editor, which is JCE in my case - everything works with that.
I liked the solution in previous versions of SPPB better, e.g. with a text add-on I was immediately directed to the installed editor (JCE in my case) - now I have to make an additional selection.
The one error is of course, as shown in my submitted pictures, that the list in your editor is destroyed - strangely, this result (second picture) is not passed on to the page itself - so the editor is not really usable at the moment.
It is also not helpful that the "class" of the paragraph above is transferred to the paragraph just created when the Enter key is pressed (this can be useful, but usually isn't).
Anyway - an editor is a basic component and should be the first to work, especially after the many updates of version 5 - 5.1.8, 5.1.9, 5.2.0, 5.2.3 - in my case
Regards