Steps to reproduce:
- Navigate to a document with a lot of content that has a scrollbar when you are in edit mode (for example Sandbox.WebHome)
- Hover over "Edit" and click on "WYSIWYG"
- Scroll to the bottom of the document
- Place the cursor at the end of the document
- Press on "Enter"
The page scrolls to the top. Also when you click on "Insert Horizontal Ruler" you get the same unwanted behaviour. I couldn't reproduce this bug on IE8/9 and Firefox.