Cannot eject USB from Optiplex 3000 on Horizon 8

Hello!

I am using an Optiplex 3000 client running ThinOS 9 to access an RDS pool on Horizon 8. 

I had configured the system so that end users on Optiplex 3000 could use (and eject) USB sticks.

I continued upgrading both Horizon and ThinOS and at some point this functionality broke and the user is asked to provide administrator credentials to eject USB sticks.

This happened some point after upgrading to Omnissa Horizon 2412. If I use the Horizon client to connect to the pool, everything is OK, so it has not to do with Horizon itself. 

It looks like it has to do with ThinOS - Horizon interaction. Problem remains for Horizon versions 2412, 2503, 2503.1. ThinOS is on version 9 and for ThinOS packages VMware_Horizon_Client_SDK 2406, Omnisa_Horizon_client_SDK 2506.

Any ideas?

Have a nice day!
Kyiakos