I have undeleted a template in de.wp, on the undeleted page I saw the unreview notice at the right top corner. Then I scrolled to the bottom of the page, but the review button was disabled and only the unreview button was enabled. I have to unreview and than review the page. Purge does not helped here.

This looks like a bug, because a undelete page in a review namespace should be marked as review (if the undelete user has review rights).

You can see the undelete/unreview/review in the log:
https://de.wikipedia.org/w/index.php?title=Spezial:Logbuch&page=Vorlage%3AImDruckVerbergen&hide_review_log=0

Version: unspecified
Severity: minor