Troubleshooting a door bell

When we got to the new house we didn't have a door bell or even a door knocker. We got one of the wireless doorbells and it was always kind of flakey.Basically whenever I was testing it in my hand it would work. When I installed it on the plate on the door frame it would work once or twice, then stop. This could repeat all day long.I tried swapping batteries.No joy.So, what could be going on?Well, my first thought was transmission problems from potential shielding from the door frame. So taking the button off the door I tested it next to the doorbell. It rang. I took it outside and tested. It rang. I put it next to the door frame. It rang. I put it almost up to the mounting plate. It rang. I attached it to the mount. It didn't.A difference of a millimeter shouldn't make a difference.I repeated this a few times. It was 100% repeatable.This can't be an RF issue. It's electrical, but not really anything complex. It has to be a mechanical electric problem.I took the battery out and futzed with the battery contact, a little bent bit of metal. I bent it out a few mm more.I tried again and it worked all the time!