midi import doesn't get any notes

I have midi files produced with Keykit. Unfortunately they don't seem readable by MuseScore: I've tried importing one short midi file, and I got over 1000 empty bars - note a single note was imported. This seems especially odd as timidity is able to play the file without any trouble. This problem is with MuseScore v. 3 and 4.

Is there some special formatting that MuseScore requires from midi files?