[GS] Worldbuilder- Can't Place Natural Wonders

[psychodropnear]

When placing natural wonders in worldbuilder I get the message "one of these already exists" even though I haven't yet placed it.
It also seems as though placing one wonder may preclude placing others. Can some natural wonders not be placed on the same map as others?
I've read that natural wonders have problems if there's ice on the map or rivers. So there are no rivers or ice when trying to place them.

 

[Victoria]

There is a wonder limit per map and they have certain placement restrictions. Not may can be next to rivers for example.