Overlapping events

Hello folks !
I have been using JEvents for years as a "room planner" with several calendars (locations), everything works fine. Now I have added 2 new calendars (locations), with exactly the same settings as the previous ones, but now JEvents reports "overlapping events" (only for the 2 new calendars), although different categories (rooms) are scheduled.
Compared all settings with the "old" ones: Menus, calendars, categories - everything is set the same.

Summary of my settings: In the calendars (Oberrad, Langen, etc) a check for overlap is displayed so that the calendars do not collide. In the respective categories (the rooms), I have switched on the check so that the appointments in a room do not overlap.
This works for the old calendars, but not for the new ones, although I have set everything the same.
I have also tested scheduling via the backend, unfortunately they also show overlapping appointments.
2 screenshots for calendar Oberrad, settings in PDF attached.
Thanks for your help in advance
Joomla 3.10.11