If you have a other pendant in hand switch pendant and observe if you have connection problems with the new pendant.
1-Look for pinch on your cable
2- Turn off our controller and unplug and plug pendant (loose connection)
3- Bad batch of pendant ( 1 or 2 pendant two year ago have some issue)
4- I did see once a cable slide-out from inside the pendant, cable restrain did not make is job.
and other cause hardware and software