w:en:User:Neil P. Quinn-WMF/T120898 has two revisions. The first contains the text "This is an old revision" while the second contains the text "This is a new revision".
Open the old revision in VE. As expected, you see the text "This is an old revision."
Now, click on the brackets icon to switch to the wikitext editor. If you've made any changes, choose to the discard them. Unexpectedly, the editor has now jumped to the newest revision of the page, so it contains the text "This is a new revision".
This doesn't happen when you've made edits in the visual editor and keep them when switching to wikitext. It also doesn't happen in the wikitext -> visual editor direction.