I have seen the Bosch controller lose the feed rate setting.
In the PLC the part that reads the feed rate pot got screwed up because of unexpected sequences with limit switches. Problem appears to be earth/noise problem. Make sure all the cable shields are connected properly. (usually at one end only).
Sounds like earthing problem at pendant or where FEED pot is located.
I suspect that during the normal PLC scan, the feed pot has been read incorrectly. There also could be a noise spike from some other fault coincident with the reading of the pot.
I notice on this controller, the feed pot is also sampled when manual control is selected to/from remote jogging. This sometimes read the wrong value. Again
bad earthing fixed it.