Just to be clear, what I’m suggesting is to use the Moxa hub without external power, or swapping in any old USB2.0 hub. What I’m wondering is if the problem is related to the stick continuing to have power. I’m grasping at straws with this, but just trying to work through hardware variables.
There’s no point to testing with the Gen5 stick plugged in directly, as that’s known to be a problem.
Have you tried it on an RPi3? I’m just curious if you’ll see the same behaviour.
I think what I’m missing is why the dirty shutdowns are happening. I assumed that you were trying to plan ahead for power failures, but you mentioned that you also have a UPS. If the UPS has a USB connection, you can use NUT to execute a graceful shutdown whenever the battery is nearly depleted. As you noted earlier, the only issue is that the RPi won’t turn itself back on afterward, but that’s only going to happen whenever you have hours-long outages.
It now sounds like you’re intentionally unplugging the RPi while it’s running and expecting it to be okay afterward. In which case, yes, add a switch to do a graceful shutdown.
The thing is, it shouldn’t be. I have a Zooz USB stick in an RPi4, and it gives me absolutely no trouble at all. Since you’re running a fresh OH, I’m inclined to think the problem is your Gen5.
New question: how far is your remote RPi from your server? If it’s in the same building, you could just put in Z-Wave plugs/switches to act as a repeaters. That has diminishing returns, but may be easier and more reliable in the long run.