Video Bug witth Audio?

Soi just started Video editing and wanted to use somthing simple first. So i picked up SHotcut. But now i problem accured ( tried already with restarting didnt help.

So when i am putting cuts in, normal or per example editing a Text in the Video, it stuttert a lot. First it was just one short piece and was ignorable, but now it is happining every new cut.

This is typical preview quality. Export is better. Take it or leave it.