We rarely stall with PR's - this is probably due to the 5 forward/3 back and constantly changing supplemental work and focus.
Understand that the 5/3/1 program is hard and you can't keep doing the same thing over and over again. So while the principles are solid, you have to approach things a bit differently - thus the different variations. For example, and this is a worn out cliche, but eating X amount of food to get to x weight/strength only works for awhile. At some point, you gotta feed the engine more gas. Too many times people expect the same stuff to work that got them from 300-400 pound squat. it just doesn't work that way.
And that is why it is hard to get stronger once you get to a certain point.