Can anyone having this problem try out this workaround?
From the Dashboard:
1. Click Posts then from the Edit Posts table, find a Post that you know is big enough to need to be scrolled in the editor window. Hover you mouse over the title of the post and click the Edit prompt that appears.
2. Once in the editor, click HTML .
3. Click Dashboard and if asked, confirm that you want to abandon editing.
4. Repeat step 1.
I find that the post is now editable without any jumping.