I found that a few of the SE's, when the body was put on, would do something similar. There was a solder joint on the bottom of the pcb that would compress down and touch one of the metal connections going to the motor.

I think you solved your problem, but this still might be a cause for you. Reseating the motor might just have moved the pcb a little.

Welcome to the forums, and I appreciate you linking to a thread that helped and editing your post rather than posting a new one.