Hi, Pal..
If the robot stop is at the same position, probably your problem is the cable, is hard, i know, but its fast to replace... so, if you don't have the spare part, you need to take out the cable, check all cable (connection, isolation, wires, etc)... otherwise check the stress and bending of cable in that position, sometimes is broken inside, or connections are loose.
In strange cases, I changed the connection from control to mechanical unit, because the cable is broken inside, why?... because sometimes they have stress on the connection and routing, in some cases there is extreme enviroment.
I hope that help you to solve the problem, anyway be patient.