RDP disconnections over Forticlient SSL VPN in tunnel mode.

Hi all.

I'm experiencing a strange issue where we are constantly getting RDP disconnections or timeouts to a client's Windows hosts when connecting to the network through Forticlient. The remote machines are still reachable via ping during the timeouts with no packet loss. The issue is consistent with all remote VPN users. 

The VPN config is straight forward. The VPN is listening on a custom port and there is a single inbound policy allowing addresses from SSLVPN_TUNNEL_ADDR1 to the internal network, no NAT, no UTM features.

Any advise will be appreciated.

Thanks.