See 8:13 in that video:
Guys, you should repair this. Why do we have to instant delete all keyframes from "picture in picture" mode and apply "picture in picture" effect again to these feature (motion tracking) works?

I want to set my lower third for example. But after that my lower third IS ALWAYS in a wrong place, for example is too smal and we are UNABLE to scale this. All we have to do is just delete "picture in picture" effect and apply the same effects again. Then we have an opportunity to changa a scale/resize our lower third.

Don't you think that is a bug or rash (ill-considered) feature?
Just watch a couple second of that video. It shows all. Any creator of Vegas 21 here?