While I can confirm that this issue exists, unfortunately I don't envisage there being a quick fix for it.
I believe it is fixed (or at least behaves slightly better) in XenForo 2.2 (which uses Froala v3). However, because Froala v3 exists, there doesn't appear to be much urgency in terms of maintaining the existing v2 branch and will soon reach a stage where it receives no further updates.
While this is unfortunate, I do not believe the issue to be quite as extreme as you describe and there is a workaround.
From your video, you are trying to access editor buttons without the editor being focused (no cursor in the editor, no keyboard displayed). This does indeed produce the behaviour you describe, but as a workaround it seems as if you focus the editor first, and then click the editor button, the page doesn't scroll.