I quote myself from Scenes/Parts bug with pickup track
If memory serves and based on what has been written in this thread, the “problem” is that the tracks don’t look up the current part until they are trigged. PU tracks don’t have trigs. Manually trigging the offending track via buttons 9-16 seems to have updated the track to work with the currently active part.
Mind you, in most cases it is probably better to handle the track/part relationship this way.