I am having a problem with a model. I imported the models and they have holes in them. I’m not sure why this is happening. I have attached a picture. I tried reimporting the models but that didnt help. Thanks
have you checked if your normals are ok?
if some polygon normals face backwards then they appear as a hole
try and view the model from the opposite side
if those are visible when you do that
then you must go to your 3d editing program and unify the normals 
if thats not the case
maybe those polygons somehow detached from the main mesh
i hope you will solve your problem
make your model triangulated… that usually helps. I had similiar problems on a character of mine… a 5 sided poly on my character was going invisible , im guessing it never exported through.