So, I use Movie Studio Platinum 14 (build 148) and up to recently this was not a problem... but then for some transitions, like for example "Slide out" a yellow line follows the frame that slides out. Pretty much like if you imagine there a yellow line just outside the screen that becomes visible as the slide out occurs.

I really don't have any explanation to why this started, could it be I have activated something by mistake? Included a screenshot where you can see that yellow line...