Its only happened with Bambu PC filament, admitedly its the only PC filament Ive tried so far with the X1C. Its definitely not a nozzle clog or extruder sound. As to why I retension the belts after each instance of this, its to make absolutely sure they are back to correct tension since the noises are awful and I get the resonance frequency error messsage regarding calibration. In the past I have tried to just recalibrated and sometimes it doesnt remove the error message but performing the maintanence does. I dont clean the rods every time, only if I get the specific error message for it or a month has passed. I rarely print with ABS/ASA so they dont need a ton of cleaning usually.
I dont have video, but someone else just made a thread with a very similar if not identical problem (with video), except they were using ASA or Nylon. Interestingly, I have not had this issue using PA6-GF. I do wonder if the 110c bed temp and 50c - 55c chamber temp is having something to do with this.
The link to their thread is here Problem with Y,X stepper motors (probably)
I will try to get the GCode comparison for you shortly