If you have problem with Robe fixtures, go to the Robe and harass them about it. ;)
They try to make their own fixture files, and they are co-founder of GDTF format (while it's actually expansion of gMA2 fixture file).

Many fixtures are troublesome with MA 3D rendering, but that's limitation of current MA 3D, and it's unlikely to be addressed (because chinese copycats and pirates).
You can expect those issues to be addressed with GDTF in grandMA3.