Masquerade in GRE

Hi
I’m setting up 2 routers and 2 networks behind them. I am raising the GRE channel through an additional virtual IP address. I’m setting up routing. ping between network computers works, RDP works, but does not open shared folders. If in the NAT masquerading rule I add masquerading to the Bridge interface, then everything works. What could be the problem? What am I missing?