edited buildings not saving in gem

[djsatane]

Where are you saving it? remember that original maps are within pak files, save the map as something else under map folder and open that see what happens.

What you doing is fine and I done that many times that normally works fine, but your problem I bet is the fact you not saving it properly or to proper file. Try to extract that map from pak file and name it something else even then edit it and save. Or you could create a mod and edit it under mod folder.