Don’t quote me because it was some time ago but I think it may have been resonance in the lead screw not the motor. Resonance amplifying vibrations in the lead screw leading the machine binding and stopping the motor, not a problem directly in the motor. That’s my recollection anyway. I think that it’s important to have the lead screw under tension from the nut at the end, probably more so with the 48" machine. I believe the tension helps with the vibration or ‘whip’ as I’ve heard it called.
EDIT: Searched the forum for resonance and got some hits. This thread seems relevant and it led me to this article which I think is what I was recalling the resonance thing from, so not a video after all. Chris mentioned in the first link that the new drivers on the SLB don’t cause as much vibration in the motors, and thus the whole machine, so maybe the whole resonance idea is off track.