Intermittant rf key issue

[Iceman299]

broken track/make and break contact??  use a magnifying glass to check for breakage.......unit was dropped so suspect something heavyish ??  mounted on the circuit board..........long shot but........  how is battery contact??

It works completely fine when dismantled without issue until i put it all back together. Just the circuit board on it's own works without issue. It's when i start putting it all back together it sometimes stops working. Sometimes stops straight away or after a single successfull attempt it stops.

At times it's when i put the key in to a fully assembled fob it stops working, other times it works fine with the key and one bottom cover but stops when i put the top cover on. 

I just can't see how either a key blade or plastic fob covers would prevent it working