Yesterday, 5 of my questions were downvoted within 2 minutes on one Stack Exchange website (askubuntu). I didn't pay much attention to it as I thought that it would get detected as serial downvote, and therefore reversed.
Instead, my questions were deleted, due to the auto-delete script aka roomba (the questions were a bit more than 1 year-old).
Why didn't the votes get reversed, and is that how Stack Exchange is supposed to work?
Following Nicael's answer, there seems to be some conflict between the reversal script and roomba: the votes did get reversed, but the questions got removed nevertheless:
Update 2016-12-24: the issue is still present.