In object maker, load the objects that occur in your map but save them in a new objects list. Something easy to remember. Do this for every object that appears in the new map.
When all are converted to the new map, in the files for feral heart find the folder for your map and open it's object list. Every new mesh is listed as [location/name]. change the location to match the new object list you just created. save your changes.
Open the new map in mapmaker. If objects fail to appear, there is a spelling error in the object file for the map. Correct it if such an error occured.
If everything is as it should be (all meshes appear where you had them originally) then re-export the map.
When creating a new map, and you intend to export it for sharing, you MUST create a new objects list. You can NOT export the default objects.