I found the sollution in all xplane aircrafts refering freezes and stutters. You need to use any program that constantly use your hard drive, but not too much.
Take a big ,several gbs, file and start to download it, but make limitations of download speed. This file must be on the same hard drive, where xplane is.
No stutters, while working whith fms or changes views.
The same works whis prepare3d.