Excellent video.
I’m really tired, so this is going to sound grouchy, but I’m not grouchy I’m just tired.
It’s the range. And it’s the metal door. It’s not complicated. Those are inexpensive sensors and they just don’t have the power to handle what you’re asking them to do.
Normally when we lay out Zwave battery powered devices (not zwave plus), we assume about 12 m of range. I think you’ve clearly gone beyond that. And the metal door itself will cut signal probably 40%. Maybe more.
Ideally, you would put 2 zwave repeaters in every room. That would give you a really nice strong mesh. So in the video, there would be one repeater in the kitchen, and another over by the doors to the outside.
With the current generation of Z wave, pretty much any mains powered device except a smoke sensor also acts as a repeater. That includes light switches, plug-in pocket sockets, plug-in sensors, In wall relays, etc.
You just need to add a repeating device in the kitchen and you’re probably solve the problem.
The metal door is an entirely different issue because it’s going to completely screw up that particular kind of sensor after a week or two . Here’s the FAQ on that. But that’s actually a separate issue than the range.
Here’s some more stuff on range and repeaters. But basically you’re just asking it to go longer than it’s designed to. Zwave and zigbee devices are intended to be very low power which is what gives you the one to two year battery life.
http://thingsthataresmart.wiki/index.php?title=Repeaters
If you want longer range without putting in repeating devices, you’ll have to go to a different protocol. The Kumostat wireless tags can do it. But they cost more money and the interaction with SmartThings is a little more fragile. And the metal door still has the same problem.
Anyway, nothing wrong with the Z wave radio, nothing wrong with the hub, you’ve just gone too far for a single hop with that particular sensor. 