HA 2021.12, KVM virtualized, Conbee2 passthrough drops from guest when configured with ZHA

I’ve got the following problem: I tried a new install of current HaOS in a virtual machine from haos_ova-7.1.qcow2.xz as described in install instructions, in a virt-manager managed KVM instance, UEFI, 2GB RAM, 2 cores, on a Zotac NUC lookalike. Everything works out as expected, but I can’t get my Conbee2 zigbee stick to work.

The stick works on phoscon (and did for some time in practical use, so I suppose it is not broken, hardware-wise), shows up on the host (with lsusb), can be passed through with virt-manager to the guest. Shows up on the guest (I installed the ssh extension and looked with lsusb, and with dmesg), there is a /dev/ttyACM0 device in the guest.

When I start the configuration workflow for “Zigbee Home Automation” it is detected, but in the third step of this workflow, the long device string is not found. When I look, the stick has been dropped from the guest’s USB bus by then. I tried different ports (front/back, USB2/USB3), I use a good 1m cable to position the stick a bit away from the PC.

Any ideas/hints?

Screenshot from 2022-01-17 09-31-18

Thanks in advance, Ralph