I have a similar set up. Server in a rack in the basement, with a long cable connecting the zwave USB dongle such that the dongle is near some open framing (it’s a wood frame house). I have zwave devices in the basement, first floor, second floor, third floor, and detached garage. Maybe I’m just lucky, but the only device where I have intermittent connectivity is the contact closure sensor inside a metal mailbox located outside the house. At some point I’ll probably move that sensor to the outside bottom of the mailbox.
