Well, I tried starting with the first step in Debugging. Naturally, as soon as I got it all set up with the debug settings and DebugView++ -- it started working correctly... So I could not reproduce the problem.
the only other thing I can think of that might be related to the restoration of the feature is that I meanwhile also installed the newest alpha of Everything 1.5 (which also gets change notifications from Windows).
FYI, I had the problem for several days during which I went through multiple reboots, as well as a Windows update. Explorer and Everything continued to work flawlessly with auto-updating as things changed in the file system.
Now the problem in dopus is gone. If it returns, I will add to this thread (if appropriate).