(Feel free to improve the title. I'm just reporting from de.wiki:)

How to reproduce:

*go to some article in which the current version is not sighted

*make an edit to the article using Visual Editor, set checkmark to the option Sichte die letzten Änderungen and save the edit

*now the message appears: 1 Änderung dieser Version ist noch nicht gesichtet. with the diff from the last sighted to the new current version and with the button Sichten at the bottom of the page. (There should be a button Entsichten)

*when you look at the article history (in a new browser tab) you can see that the new current version is sighted, but the second most recent version is left not sighted (well done)

*click the button Sichten

*now the second most recent version is sighted too, although we haven't seen the diff to this version, but to the new current version. And there is no need to sight the second last version. --Diwas, 00:35, 9. Mai 2016 (CEST)