A few years back, I ordered a Kossel 2020 rev A, and, although I assembled it almost all the way back then, I'm only now getting around to actually configuring it.
One of the things I've noticed is that one of the belts isn't tracking correctly on the pair of upper idler bearing. Whenever I re-home the printer, the belt keeps shifting toward the 2020 rail, starts rubbing on the plastic, develops too much friction, and then the stepper motor stalls and the carriage never reaches the stop.
I suspect the idlers aren't as perpendicular to the belt as they should be. Does anybody know of a fix for this? If not, I think the first thing I'll try to design is a little bobbin sleeve that slips snugly over the bearings to provide little side-rails to keep the belt tracking properly.