Comment 6 for bug 2002771

After investigating that bug - using gdb and libvirt debug logs (https://libvirt.org/kbase/debuglogs.html), I haven't noticed anything suspicious that would affect ownership restoration.
From here, I'd recommend forwarding that issue upstream.
They might have deeper, more specific knowledge to help with fixing that.
Moreover, the next argument against doing that and not fixing it straight away is that the workaround exists for that issue, and fixing it directly in Ubuntu - taking into consideration and taking a look -> https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/691590 - it possibly require a change within the control or rules files, which would not be recommended in that regard because those files are important to be equal "everywhere".

WDYT @Christian?