RRAS Site to Site PPTP with Demand Dial Won't connect with NAT Enabled on branch network

Question

I have successfully setup a Site to Site connection between two remote Windows 2016 RRAS servers (branch network to remote network).

My problem is when I enable NAT on public interface of WAN adapter on branch network, the demand dial connection won't connect. Error states "Unreachable". However, if I delete the NAT on WAN interface, the demand dial connection connects to remote network successfully. I then recreate NAT on WAN interface, and everything works - client machines on Branch network behind NAT can get to internet and also have access to remote network.

Any ideas why the demand dial interface on branch network won't connect when WAN interface has NAT is enabled in RRAS?

Thanks in advance.