Something strange just happened. I noticed that my reputation had dropped by $40$ points. I went to the reputation page and saw four "unupvotes", all within one minute, on four different answers, some but not all of which were thematically related. This seemed strange enough in itself, so I went to the four answers.
One thing I noticed was that on all four answers, when I clicked on the vote tally to see the upvotes and downvotes, the vote tally went down by one. I presume that this is due to some delays in the system that caused outdated vote tallies to be displayed at first. While I find such inconsistencies slightly annoying and would encourage some efforts to prevent them, that's not my main point.
What I don't understand is why upvotes could be retracted on the three questions How to prove absolute summability of sinc function?, Aliasing in DFT: mathematical expression and On the absolute integrability of Bessel functions, since these had never been edited. Are votes no longer being locked in after a couple of minutes until the next edit? Or is this perhaps the effect of an account being closed? Or is it a bug in action?
Here's a screen shot of the reputation page: