This happened on MediaWiki, he.wiki and en.wiki on Chrome.
Open some article for editing (preferably a long one so the effect is seen)
add some text in the middle or end, mark it and make it a "Heading".
Observed result: The text turns into a heading, but the entire edit section scrolls up to the top of the page. This is especially annoying when the page is long and when the edit is done in the middle.