all events in level BP fire twice, any idea what to do?

I believe this must be some bug in UE 4.21.1 - I have a level in which events are fired twice. Even the simplest OnBegin does that. Any advice? Shutting down and restarting the editor doesn’t help. Other levels in the project seem to be unaffected.

I believe output log contains some hint, but I have no idea what it means (what are [Level044_C_107] and [Level044_C_9]?). Two separate instances of the level BP being compiled/executed?