It sounds like you need both the remote network to have NAT for you and the remote side also has an overlap with your server network and needs to NAT as well.
If that is the case then the NAT must occur on both your side and the remote side of the tunnel where you each do a full replacement for the connection to work. This is the screenOS example showing both sides.
file:///Users/stevepuluka/Downloads/ScreenOS_VPN_with_Overlapping_Subnets.pdf