Question "Destination array is not long enough" when trying to import 16 bit terrain

I have a raw terrain file that I exported from world machine, but when i try to import it as terrain it gives me this:

ArgumentException: Destination array is not long enough to copy all the items in the collection. Check array index and length.

It works if i import it as 8 bit, but then the terrain looks all terraced and gross. What's going on and how do i fix this?