@atticuscull, @pg132, @DunDunDunDone, and @modderme123 have found a bug in [Decider] Backward reasoning, see Backtracking Bug · Issue #1 · bbchallenge/bbchallenge-deciders · GitHub.
In consequence all the machines decided by this decider (1,253,418) are back to being undecided and the index of undecided machines has been updated accordingly.
Note that now, the index of undecided machines is stored on github: GitHub - bbchallenge/bbchallenge-undecided-index: Keeps track of the successive versions of the undecided machines index file of the busy beaver challenge.
This will give us an easy way to keep track of the index’s versions and restore older versions if (like what happened today) a bug is found in one of the deciders that was applied.
Update: Having discarded (until the decider is fixed) all the backward-reasoning decided machines, we re-ran [Decider] Translated cyclers and we found 1318 new ones (out of 3,575,540 machines tested).
(not an April fool’s joke :))