RDP through PPTP connections

Hi there

I hope someone could shed some light on this for me.

I have a mikrotik where we have setup 2 VPN connections, using windows 7,8 and 10, I create PPTP connections from two machines.
I can ping from PC1 to PC2 via the VPN IP addresses,

When i try to RDP (Windows remote desktop) it connects to PC 2 just fine, but as soon as I put in my username and password, the RDP session drops and so does the VPN connection.
Both PC’s have the use default gateway unchecked.

Is there a setting on the Mikrotik that im missing?
Is is due to the MTU size?

Why is the RDP session causing the VPN to disconnect?

Settings on the Mikrotik

PPTP is Enabled
Max MTU = 1500
MAx MRU = 1500
MRRU = none
Keepalive timeout = 5
Default Profile =default
Authentication = all checked