problems with USB Server and VPN

I´m trying to implement virtualhere over a VPN service (OpenVPN)

I´m runnig a VPN service and a remote SSH access and the virtualhere service as well.

I´m trying to access my RPI connected to a PLC with prolific usb to serial cable.

It works for only a few seconds and then it desconects.

The VPN (OpenVPN client) and the SSH (Putty) conecctions works relatively fine. They eventually disconnects too but with a much lower frequency.

I´m trying to understand if it is a compatibility problem between VPN and virtual here or if it is some kind of "stability network" issue.

Thanks,

Patricio