UI alignment problem

Hi! My team and I are having trouble with our project´s UI. Most of it scales perfectly when changing window sizes in unity, but some windows seem to move when rescaling, even though they are children of the main canvas, which scales perfectly. Does anyone know a fix?

Link to a video showcasing what happens:

 

Have you correctly set up the CanvasScaler to scale with a reference screen size?

If so, then it's an anchoring issue.