Reported by [[de:User:XanonymusX]] with this edit.
While loading the Revision Slider the URL the diff is rewritten from
https://de.wikipedia.org/w/index.php?title=Wikipedia:Fragen_zur_Wikipedia&curid=6977098&diff=156602018&oldid=156601953
to
https://de.wikipedia.org/w/index.php?diff=156602018&oldid=156601953
Therefore the browser history is increased by the rewritten URL and going back per browser needs 2 clicks instead of 1 as usual.