The RX 7600 XT guest stopped responding again. The VM list still looked reassuring. A closer status check reported an internal error.
This time the card was still on the PCI bus. Stopping the guest worked. Starting it with the GPU attached did not. The host reboot brought inference back.
The failure happened while idle, which weakened the earlier theory about load being the trigger. Firmware polling and runtime power management became the next things to test. They are a working hypothesis, not a proven cause.
The practical lesson: “running” is a process state. It is not a health check. A small inference request tells me more than the green status label.