Y axis occasionally jamming  

Y axis occasionally jamming

Hey guys, I tried searching posts for my issue but I couldnt find anything quickly.  I have been having some issues where my y axis (forward and back) when looking at the front of the printer, gets jammed, and the printer doesnt know this happens.  I tried removing the belt and checking to make sure everything runs smooth, and I cant feel anything that would cause this.  I read somewhere that the bearings need to be repacked?  If that is the case, are there instructions?  Maybe one of the ball bearings in the bearing assembly has a flat spot?  If so would repacking help solve that issue?  Should I just replace all three bearings?  This printer has been running for about 1.5 years, and this jamming has been happening for the last 6 months on about 1 of every 10 prints (more prone to happen on larger y axis objects, than small things).

Thanks in advance.