Offset points shifting

Hello all,

We’ve had a UR5 e-series robot picking connectors from a set of shelfs where we’ve taught the first position for each shelf which have 20 pick positions. For the rest 19 we’ve used a PLC offset system where the robot will find the offsets through the use of a PLC offset system. The system has been running fine for a year now with the odd tweaking here and there.

However for the last few days the offset values keep changing every time the robot goes to pick from that position. The PLC code hasn’t changed and believe it could be something to do with the UR. Anyone come across this sort of problem before?