Hey guys, so I've been working on a set of custom animations for the SVG-100 sniper rifle from BO3. Initially, I received the model as one whole mesh, which was fine as I could weight-paint it (though that was a tough job). I was able to make and export all the anims with no problems whatsoever, but I got the "too many verts" error when trying to export, which I guess was caused by the model being so detailed. Simplifying the model wasn't an option as using that tool would fuck up the mesh beyond all recognition.
So the solution I tried to use was to select the mesh, then use Edit Polygon > Separate to split it into a whole bunch of pieces, and then combine them into about 12 pieces to hopefully eliminate the error and make re-rigging easier. It seemed to work, but there were two main problems that I have no idea how to solve. When trying to press 5 for smooth shading, Maya would crash for certain meshes such as those of the clip and main gun body. Also I would get this error when trying to export the model into .XMODEL_EXPORT format:
Error: Internal failure: C:/Users/Colin_2/Documents/maya/projects/default/scenes/BLACK OPS 3/SVG-100/viewmodel_svg100.mb.XMODEL_EXPORT

Does anyone know what these errors are, and how to fix them?
If not, are there any possible alternative methods to fix the "too many verts" problem?