hardware debugging - cordless door-bell

A cordless door-bell which K got for me had a funny problem. When I affix the remote switch on our door, it would not work. Remove the switch from the door, and it works, though it is at the same distance from the bell. When KR fixed it to the wall instead, it worked. So, in retrospect, it was probably some sort of capacitive effect from the aluminium door frame acting through the plastic case which was changing the transmission frequency or something.