every time I try to export via .fbx I get this error. 
What I was doing: I have a project I'm working on that needs constant tweaking in the game engine, but this engine only accepts .fbx, so I can keep all the modifiers live and iterate if needed. This engine also requires that every mesh/object have a material assigned to it via the 3d software before export, and because I wasn't done working on the file I thought I would assign a temporary material called !Pink and assigned it to all the objects in the scene that didn't have a material assigned to them. Well, the engine did not accept the question mark in front of the word as a valid material name. So I decided I was going to finish up the project and assign proper names to each and every object. That left me with Orphan Data, so I purged those materials and tried to export again to .fbx, and now I am getting this error.
Python: Traceback (most recent call last): File "C:\Program Files (x86)\Steam\steamapps\common\Blender\4.0\scripts\addons\io_scene_fbx_init_.py", line 663, in execute return export_fbx_bin.save(self, context, **keywords) File "C:\Program Files (x86)\Steam\steamapps\common\Blender\4.0\scripts\addons\io_scene_fbx\export_fbx_bin.py", line 3627, in save ret = save_single(operator, context.scene, depsgraph, filepath, **kwargs_mod) File "C:\Program Files (x86)\Steam\steamapps\common\Blender\4.0\scripts\addons\io_scene_fbx\export_fbx_bin.py", line 3510, in save_single fbx_objects_elements(root, scene_data) File "C:\Program Files (x86)\Steam\steamapps\common\Blender\4.0\scripts\addons\io_scene_fbx\export_fbx_bin.py", line 3307, in fbx_objects_elements fbx_data_mesh_elements(objects, me_obj, scene_data, done_meshes) File "C:\Program Files (x86)\Steam\steamapps\common\Blender\4.0\scripts\addons\io_scene_fbx\export_fbx_bin.py", line 1397, in fbx_data_mesh_elements raise RuntimeError("UV layer %s on %r has invalid UVs containing NaN values" % (uvlayer.name, me)) RuntimeError: UV layer UVMap on bpy.data.meshes['Mesh.052'] has invalid UVs containing NaN values
Also, every time I purge the Orphan Data and try to export these 50+ meshes they reappear in the list with different names "mesh.01, mesh.02" etc even though i didn't have any objects with that naming convention. These are the meshes I applied the same !Pink material to:
And this is my objects list none of these objects have the name 'mesh' in them, they are all numbers:
Ctrl+D, the new object is named "Cube.001" (because no two objects can have the same name) as well as the mesh data. But a linked duplicate withAlt+Dwill have the object name "Cube.001", but the mesh data is still "Cube" (with 2 behind the name field) because two objects use it. $\endgroup$