I had a track shifted, scaled, shadowed, etc., using track motion.

Happily editing away, adding clips to the track etc. etc.

Suddenly, the track motion settings stopped working. They were still set correctly, but not being applied to the clips.

Other tracks in the project that used TM remained fine.

I finally had to create a new video track, reproduce the TM settings, and move the clips onto the new track, where everyting worked fine.

I could find no setting anywere which looked like it would disable TM settings. Is there one that I missed somewhere?