Exported .stl files are fail integrity but the original was ok, why?


I Think I have discovered (at least one reason) why I am having so many print fails. I model in 3ds Max 2014 as a polygon model and then export as .stl. Having noticed that models which were completely intact as poly models (I used an stl modifier to check the model integrity) were opening in Preform with issues I checked out the stl exports and guess what, they were full of errors (primarily border errors).

Anyone got any thoughts on why this would be the case?