Boole failed

 From:  Lara (MALA)
10128.1 
Hi, the bool between a ring and a shpere does not work:
I would like to cut a ball segment out of the ring. But the operation is not completed. The calculation process continues and is not ended.
Situation: Although it is a connected object, I can select segments of it individually in the working window, see picture.
Is that something related? And how do I connect correctly?
A test with another ring worked immediately.




EDITED: 10 Feb 2021 by MALA