Everything is fine here except 2 things:
1: As I mentioned earlier both side should have proxy id 0.0.0.0/0 configured, not only one side. Please check other side proxy id.
2: You policy ordering and policy objects should be like below:
A: set policy from "vpn" to "Trust" "corporate-hosted" "MIP(172.21.1.1/24)" "ANY" permit <-- this should be first and I am not sure why vendor-server is not added here either add it here or you need to create a different policy to allow traffic from vendor-server to Trust, with or without MIP. If you are creating MIP policy for the vendor-server then it should come before the policy which is there in "B".
B: set policy from "Trust" to "vpn" "local-net" "corporate-hosted" "ANY" permit <-- this should be second and again vendor-server is missing here.
C: set policy from "Trust" to "Untrust" "Any" "Any" "ANY" permit
Note: You can change the policy order from GUI easily.
Thanks,
Vikas