I recently replaced my UPS and set up NUT (Network UPS Tools) for monitoring.

Everything works fine for a short time, but after a few hours, NUT reports “error: Data stale” in the web UI. After a few more hours, the web UI just stops responding completely.

I have NUT running on a Ubuntu VM in Proxmox. My UPS is a Tripp Lite (Eaton) SU1000RTXL2UA. It’s connected to my hypervisor via USB and passed through to the VM. Restarting the container fixes the problem. Any idea what could be causing this?

Update:

I noticed this problem while I was troubleshooting another issue, but it seems to have fixed my issue with NUT as well. Seems like there is something wrong with USB3. The server itself has several USB2 ports, and I installed a PCIe USB3 adapter. USB2 devices plugged into my USB3 adapter lose connection after a period of time. What makes it even stranger is that when I pass through a USB device and select the “USB3” checkbox, it causes the same problem, even if the device is physically connected to a USB2 port. I had 5 devices connected to my PCIe card, and they all started working perfectly after I plugged them into the USB2 ports on the server’s motherboard. My UPS was already connected to one of these USB2 ports, but I had USB3 enabled in Proxmox. As soon as I disabled it, the problems with NUT disappeared.

I don’t have a good explanation for why both my USB3 PCIe card and the USB3 option in Proxmox don’t work, but the problem seems to be fixed for now.