As I'm in the process of switching from Samsung SmartThings to Home-Assistant for my home automation, I've been re-pairing various Zigbee and Zwave devices.
One of those devices, a Samjin button, branded as SmartThings wouldn't come back to life after I removed the back cover (it was too tight against the wall to reach the reset switch). I recall having two buttons in a pack of 5 that also did the same thing. Those two seems to be dead-on-arrival, but I knew this button had been working fine. After much fiddling, I managed to coax it back to life by holding the CR2450 battery in with one finger. Whenever i put it back onto its battery cover however, dead.
No amount of bending the battery contacts made any difference. So, I put a tiny square of folded tissue paper behind the battery (between it and the rear cover where the magnets are. Hey presto - immediately works. Slightly snug to twist the battery cover on, but I now think I know what was 'wrong' with those original two buttons which went back to Amazon...