Help With Model Rendering/Formatting

Hi all, I have been trying to add OSRS models to my 718 server. I have had success with all models I've gone through so far, but this one just isn't working for me.

So basically, my process is as follows:
1. Import .obj and .mtl into Metasequoia, and then export as .mqo
2. Open .mqo file in DatMaker and then export as .dat

Now, the problem is, when opening this model in the DatMaker, it seems to loose a lot of it's triangles, or pieces. I have provided an image below of the model looking perfectly fine in Metasequoia, but then breaking in DatMaker.

Any help with this problem would be greatly appreciated thanks.