Otis 411 big posi slip

I have an Otis E411MMS gearless that keeps getting a big posi slip fault (2700) in the down only it seems, somewhere around the half way most of the time anyway. I've checked encoder seems to be counting ok, door zone switch and Ld and Lu seem to be coming on and off ok. I'm fairly positive it's not actually slipping, it's double wrapped. I've checked encoder coupling it's tight and didn't seem to have any Knicks or tears. The slip tolerance is set to 400 which is around where most of the other cars in the bank are set. I've tried reducing acceleration as well as the ratio. And performing a learn run. I can't seem to pin point what's going on. Any suggestions? Should I do a learn anytime I adjust anything in the profile is that necessary?

Thanks in advance.

Quick edit it's actually a 2100 fault not 2700.

Are there any other faults showing up along with that? It does seem unlikely but worth marking the rope and sheave and making a run down and back through that section of the hoistway to be sure it isn’t slipping traction.