One thing that every adaptation of Dune seems to get wrong: throughout the book series, the Fremen are always described as wearing robes covering their stillsuits. And a passage in God Emperor of Dune makes clear that “covering” means completely covering:
The grey slick of a stillsuit could be seen underneath, exposed to sunlight which no real Fremen would ever have let touch his stillsuit that way.
In the 1984 adaptation, the Fremen wore no robes at all. In the 2000 adaptation, they usually wore robes, but seldom entirely covering their stillsuits. The upcoming 2020 adaptation looks like we’re getting exposed stillsuits once again.