It's not the belt or a jam or anything (read through my various replies here for more details on it, that video shows the motor behavior after starting a print job and cancelling)--the motor operates perfectly fine when jogging or manually moving it around, and even on a print job for a smaller STL file. I think the problem is software-based, which is what my whole other thread is about--I posted two separate threads thinking I was having two problems but the more I dig into it the more I'm realizing they're related.