OK, what you gave me works fine, but I guess I need that fifth part after all.
The four parts don't add up to make the whole model, so the last part is still needed.
Can you try different combinations of deleting parts in TOOL until you can get the fifth part isolated, even if it still has another part with it?
The trouble is getting something which is less than 50,000 faces, but even if it's slightly over, hopefully things should still work out.
Anything over 50,000 doesn't export to OBJ very well, but the 'mess' it makes depends on how far over that limit a model goes.
The four parts don't add up to make the whole model, so the last part is still needed.
Can you try different combinations of deleting parts in TOOL until you can get the fifth part isolated, even if it still has another part with it?
The trouble is getting something which is less than 50,000 faces, but even if it's slightly over, hopefully things should still work out.
Anything over 50,000 doesn't export to OBJ very well, but the 'mess' it makes depends on how far over that limit a model goes.