PSA - "creaking"/"squealing" sound and reloading the filament fixed
I was getting a significant squeaking/squealing sound from what I thought was the slide bearing/linear rail (nextruder mounting rail not the two smooth rails) and tried a few things to deal with it (checked belt tension, retensioned from scratch to get the tiny bit of play I had in it from building the kit, let the smooth rail bearings reseat themselves by loosening screws, wiped off remaining excess oil on linear rail, and a few other things).
Continued the print, banged my head against the wall a bit, while banging my head against the wall, noticed the squeak stopped while it was moving but not extruding. Unloaded the filament, cut ~3 inches off, reloaded, and the sounds were all gone...
Putting this out there in case anyone else comes across the same sounds I did (sorry, but didn't catch a video, was about to after I finished banging my head against the wall).
A description in case it helps identify for anyone else: Two sounds were happening at the same time. A squeaking/creaking sound that had a frequency at about 5 or 6 squeaks/second when going at 100% speed, structural print, moderately high pitch. A higher pitch constant squealing sound while the nextruder was moving along the linear rail. It was somewhat intermittent in presence/intensity. When slowing down the print speed, the squeak frequency also reduced, and the squeal volume got lower.