Just to make sure it isn't just that specific map file acting up on you, I want you to try saving it in another name by doing this:
1.) Open up your map in Map Maker.
2.) Replace both the Map Name and Display Name with something new.
3.) Click Save, and this will have created a copy of your map.
4.) Try exporting it this way. Sometimes this weird trick helps.
If the trick above doesn't work, then try exporting your original map again, and look at what kind of meshes it isn't exporting.
If they are Custom meshes, which are meshes/objects you may have downloaded from the forum or a friend, I would try going through your map and removing any of the trouble-making meshes. (If you have a LOT of custom meshes that would take too long to remove one by one, you can go to Object Maker and delete the Object group causing trouble).
If it won't export any Default meshes, like the ones in "MyRocks," "MyDefaults," or so on, then it's likely that a file has derped up somewhere in your game. In that case, go to FeralHeart>>Media>>Terrains, back up your map (or any others you want to keep) by saving it in another location, and then uninstall/reinstall FeralHeart. You will likely have to re-download any unsaved mods/markings/emotes if you didn't back them up, but at least this will ensure that your default items are working properly.
