You have described exactly what I went through to a T. My z-wave mesh started to get affected also. That is, 75% of my z-wave devices would go offline and repairing would fail at those devices. Most of them were the z-wave repeaters built into my zigbee iris plugs. I read the z-wave repeater portion was a little flaky, so as part of the troubleshooting, I removed all of those. I don’t think it ever improved the mesh anyway. I installed an aeotec z-wave repeater about 5 feet from the lock and still the same disconnecting problem.
Z-wave in general has left bad taste in my mouth. I installed a z-wave garage door sensor a while back and that would give me a lot of heartache. It went offline constantly. I finally switched the sensor with a zigbee open close sensor. Now it always works.
I hope it’s not the lock itself that is the problem and not just the module. Is that burning out modules?
I ordered a used Kwikset Convert last night at a cheap price through amazon. I was going to swap out my dying z-wave module from my 910 and use the Convert’s zigbee module. Hopefully that will solve my issues.