Possible 7.3.1 regression after upgrade: Plex/Intel Arc instability + UniFi OS VM hangs

Hi all,

I upgraded this host from 7.2.x to 7.3.1 yesterday afternoon. It had been stable on 7.2.x for a long time, and these issues only began after the upgrade.

I’m seeing two separate symptoms on 7.3.1 / kernel 6.18.33-Unraid:

1) Plex instability

• Shortly after upgrading, Plex went unstable and contributed to a host failure severe enough that I had to reboot

• Plex was using Intel Battlemage / Arc hardware transcoding at the time

• Since rebooting and switching Plex transcoding back to the Intel iGPU, Plex now appears stable

• That makes me suspect either:

  • a 7.3.1 kernel / Intel driver issue

  • Battlemage / Arc-specific instability

  • or an issue with the newer Plex transcoder path interacting with the Intel stack on 7.3.1

Plex details:

• Container: plexinc/pms-docker:latest

• Digest: sha256:c37106c57fed7a6624f5dee5a3ce460ff011f09a2aa7f4ee9e8dbbd08ae1b87e

• Container OS: Ubuntu 24.04.4

• Plex logs reference intel-compute-runtime 24.52.32224.5

Example Plex log during failure:

Critical: libusb_init failed

Abort was called at 134 line in file:

... intel-compute-runtime/24.52.32224.5 ...

2) UniFi OS VM hangs

• My Ubuntu-UnifiOS VM also became unstable only after the 7.3.1 upgrade

• VM still shows running in libvirt and remains present on br0 / ARP / FDB

• The issue happens after a short period of time; I can access the VM GUI and SSH for the first few minutes after boot

• After that, SSH / web management stop responding

• In one hung capture, a single QEMU thread is pegged:

  • CPU 3/KVM ~100%

  • vcpu.3.blocking.cur=no

• I also captured net.0.rx.drop=3172

• In the minutes leading up to the hang, other non-pinned host CPU cores also spike hard, which does not happen with this VM shut down

Important:

• This happened on older UniFi versions

• I then updated UniFi OS + Network Application to latest

• Behavior did not change

What remains stable

• Windows 11 VM is stable

• Home Assistant VM is stable

• Other Docker containers are stable

• Plex appears stable now after moving transcoding off Arc/Battlemage and back to iGPU

So this does not look like a full general host failure. It looks more like a 7.3.1 regression affecting specific workloads.

Files attached

• unraid-diags-baseline-20260530-1334.zip

• unraid-diags-hang1-20260530-1351.zip

• unraid-diags-hang2-20260530-1410.zip

• unifi-vm-custom-captures-sanitized-20260530.zip

Main questions

• Does this look like a known 7.3.1 regression involving Intel Arc/Battlemage, Plex transcoding, or KVM/libvirt/virtio networking?

• Would you recommend I downgrade to 7.2.7 as the next test to confirm whether both issues disappear there?

Happy to troubleshoot further, post additional logs, or follow any recommended testing steps.

unifi-vm-custom-captures-sanitized-20260530.zip unraid-diags-baseline-20260530-1334.zip unraid-diags-hang1-20260530-1351.zip unraid-diags-hang2-20260530-1410.zip