There’s an interesting thread developing under developers on understanding and troubleshooting timing issues:
I have researched USB issues on Proxmox/KVM and found there was a bug in QEMU that was causing VM freezups - something I have experienced with Pi PICO. Given that well working USB connection is crucial for Klipper I figured the best way would be to install cheap PCIe USB3.0 host adapter and passthrough the PCIe slot to the VM. I’ll report here how well that works (I don’t see why it wouldn’t).
I don’t know the details of the USB bug to tell if it could have been causing other issues than freezups, however I think PCIe passthrough could be one way to remove any thoughts about USB being the cause.
EDIT: just confirmed: passing-through whole PCIe sunrize xHCL controller to the VM, instead of individual USB port, bypasses the USB bug as expected.