VirtualHere issues over VPN (TCP:443)

I am trying to use VirtualHere in the following scenario:

VirtualHere Server 3.2.9 (unlimited) on Synology NAS
- FTDI adapter
- USB ATmel ICE

VirtualHere Client 4.0.6 on Windows 7 x64 Enterprise

The PC client is connected to Synology NAS using a VPN (openVPN) connection on port 443, using TCP (TAP) (only 443 is available for VPN).
There are no issues with the VPN connection, the throughput is stable and around 10mbps. VirtualHere client discover the Synology Hub with all USB peripheral attached and connect to them with no problems.

The issue is when I trying to use the allocated COM ports, for example a Teraterm terminal will open and connect to the COM port associated to the FTDI cable adapter but the communication over terminal is not working (COM settings are OK).
The COM port allocated to the Atmel ICE adapter have a similar behavior with no reliable connection.

All traffic related with VirtualHere goes to the tunnel, based on Wireshark logs.

Note: Everything is working fine when connecting from a different network using a VPN (openVPN) on port 12972 UDP (TAP).

Any suggestions? Is somehow the issues related with the VPN connection type / port ?

Thank you.