I don't play Reforged but I can tell you, this is the problem that every people had always been encountered more recently. Sometimes, the imported models fail to load (you can see the green cubes and the "Could not load MDL files" yellow text or something similar). This always happened on the latest patches of Reforged. You'll also notice that when you start the World Editor, you'll get the so-called "Failed to load Environment Map" and the other issues relating to "netsafe", but those problems didn't affect the whole map. As Uncle suggests, try saving your map as a folder (File -> Save As -> Change the type to "Warcraft III Scenario Folder - Expansion"). That way, if your map can't be opened with World Editor due to the corrupted models, you can use the folder to replace the bad assets.
Make sure you have a backup of the said map, in case you still face this issues