“Has it ever happened that a previous Spelling Bee gets repeated on a later date?”
It’s fairly common for the editors of the Bee to repeat an earlier set of letters on a later date. The usual practice in these cases, though, is for them to use a different center letter in the later puzzle. The pangram (or pangrams) will be the same as before, but the change means there will still be some variation in the solution set, to help keep things interesting to veteran solvers.
However, on August 13, 2020 the editors for the first time repeated an earlier puzzle using the exact same center letter as before. Not only that, but they did it barely five weeks after the original puzzle had appeared! The twist was that in the new puzzle they began accepting a word that had been disallowed in the previous instance, increasing the number of answers in the solution set from 26 to 27.
This caught us a bit unprepared, with the consequence that for the first few hours of the day we were actually displaying the older solution set instead of the newer one. We fixed the problem as quickly as possible, and we certainly hope we won’t be caught like that with our pangrams down again.