You might wait a good while and see if it comes back after while or after it finishes importing. If it's all audio files and you have audio analysis enabled when auto-importing, that could potentially cause things like this too.
No analysis enabled, but I'll give it a try and let it run overnight.
On first startup it seems MC 26 started importing, although there were no file locations defined.
After I configured auto-import by adding file locations the problem started, I think.
All tasks in auto-import are unchecked, except for "update for external changes"
I might have been editing files in Foobar while MC was running, could that trip it up?