I am just a 5/3/1 rookie and just on my 2nd cycle. But a couple of things come to mind.
Are you really deloading and taking it easy on everything including assistance work?
Are you underdoing/overdoing your warmup?
Are you still moving forward overall and making gains in the big picture?
It's no secret that gains in this movement are slow.
If you see overall gains, don't worry about it just keep pressing forward, or in this case, upward.
Not much, but hopefully something.