I am fairly new to the UR world.
We have a pick and place application, where to robot picks up an object using force and then places it on a conveyor belt via vacuum pickup.
All is working fine, but every so often (really could not make out a pattern) I get error C283A2 - “Robot is moving when in Stop Mode”.
The robot gets stopped in certain situations (e.g. conveyor belt stops) but the error does not occur every time.
I will make a guess based on what you said. I suspect the robot is stopping due to a protective stop but it is in contact with the conveyor when this happens so the conveyor continues to move the robot when it should be stopped.
You should make sure you are not pushing against the conveyor when you are picking up or dropping off parts. If you need to use force to find the part or conveyor, make sure you are applying significantly less force than the force limit in the safety settings.