It's perfect at very close range to a powered device but temperamental at the 1m range
Given that it's a wireless device I'm not totally surprised since that part of the door seemed pretty solid. Think about the science of what it's doing, it's no different than a Wifi signal. If you bore that into pretty solid wood then it has to use that tiny battery to power a radio that will escape the wood around it - and that's only if the next device is at a perfect 90 degree angle to it. Battery devices are almost never relay devices, so this needs to talk to a nearby Z-wave device that can relay the signal and if that device is beside the door then your 3" door needs to penetrate 36" of door to get to the switch. If there are any walls at angles or floors or anything else then that's a lot of material for a signal to have to break through.
I run into this a lot with clients who put their access points in strange locations, they don't realize that it seems
like the access point is only 20 feet away but when you consider the angles of the walls and doors and the studs that are in the walls and everything else, it could be 100 feet away and heavily blocked.