Seagate Expansion 4Tb USB not recognised by front port on TS-673

[acdsosys]

I'm new to this forum so apologies if this has been covered and my search didn't find it.

I have a QNAP TS-673 [4.3.5.0760] loaded with 6x 4Tb Seagate Ironwolf drives (Raid 6) and 2x Samsung 860 Evo M.2. (Raid 1) configured as cache.
I have a QNAP TS-451+ [4.3.6.0776] loaded with 4x 4Tb Seagate Ironwolf drives. This provides backup via RTRR for the TS-673.

I plan to use 2x Seagate 4Tb Expansion USB drives for external backup.

The TS-451+ has no problem recognising the USB drives plugged into the front port.

The TS-673 recognises the USB drives plugged into the back ports (shows size, is viewable in File manager, I've set up a Hybrid Backup) but point blank refuses to register them if they are plugged into the front port. I've tried both drives

Is there a setting I'm missing somewhere?
Is this likely to be a firmware issue? It can't be hardware as the unit tells me there is an unrecognised USB device connected after a couple of minutes.

I could run a USB extension from the back but the whole point of the front USB is a 'simple one touch copy' method.

Any help gratefully received.

[dolbyman]

sounds like a bug..seen a similar issue in recent changelogs

report it to qnap via tticket

[acdsosys]

thanks for the reply, ticket duly raised