They made a change based on a Feature Request on Meta.SE. All sites are affected.
Can we raise the bar for reputation for late answers to bypass the review queue?
The feature request was accepted and raised the bar from 10 rep to 50 with a potential increase to 100 rep in the future, per the answer from Jon Ericson:
Raising the bar to 100 would require changing two variables at once. Since that would make it harder to evaluate each individual change, I'd like to try raising the reputation for getting enqueued to the Late Answer reviews to 50 and reconsider upping it to 100 at some point in the future.
According to some comments on his answer, Jon implies that this should have only affected answers that were posted within the last month... unfortunately, that seems to not be the case, so have fun reviewing and getting some badges!
@yo': Well, we are about to find out. ;-) Just to note, the answers should not be older than a month and the current spike should be temporary. – Jon Ericson♦ 33 mins ago
@JonEricson: One on C.SE from 2013 and one on PPCG from 2011. A month, eh? – El'endia Starman 32 mins ago
@JonEricson We've got hundreds of posts with "active: 2 years ago". Are you should about "answers should not be older than a month"? I smell a bug here... :D – yo' 32 mins ago
@El'endiaStarman: Looks like this is the second time in as many weeks as you've caught me making bad assumptions about how things work around here. ;-) Well, now's the time to earn that Late Answer Reviewer badge you've always wanted. – Jon Ericson♦ 27 mins ago
Hopefully, if they bump it up to 100 rep, they will fix this so that it doesn't go back to the beginning of the site as this one did... though, the numbers seem to show very few late answers from users with rep between 50 and 100, according to one of the other answers (at least on Stack Overflow).