It sounds like a Z-wave mesh issue, since you have tried three different units. Maybe try moving your hub out close to the device and see if it stays connected, if so then you can start working on building up your network. I have 4 of the Iris branded GDOs, which are the same unit. They do occasionally drop offline but for the most part they are pretty solid for me. I have quite a few Z-wave devices in my network. One GDO is probably more than 50’ from my hub. The hub is on one end of the house and the GDO is on the other. Almost every room in between has two GE Z-wave switches and I have 5 or 6 of the Iris V2 smartplugs that are Z-wave repeaters.