Defaut RDP 3389 Blocked on VPN

Good Day All

We have a ASG220 with Firmware version: 8.301, since version V.8.103 we have had an issue were we cant connect to all out Windows servers using RDP via VPN(SSL/PPTP/IPsec etc).

At the time we upgraded the firmware and experienced the issue I did not have enough time to troubleshoot and came with the quick fix of using a different port for RDP connections, of course this required changing our RDP/Terminal servers default listening port on the registry. So basically by using the diff port 4777 instead of 3389 my RDP connections work, the only thing I could think of is a firewall rule blocking 3389 however:
I have tried removing all the firewall rules and still not going thru;
I have checked the live firewall live log and I dont see any block/drop activity;

On the Internal LAN RDP works with defaults(3389) well and I checked our servers firewall its completely off. Is the a way for me to check were the packets are being dropped/blocked, at this point I think the fault is with Astaro because using the custom port 4777 RDP works.

Thanks for any assistance