It worked on some games, not others. Somehow, an index had got out-of-synch with the actual gameplay, which caused the de-whoopsing to fail. This is a brittle misfeature of the server code, motivated by a desire to keep the number of SQL queries to a minimum, which is probably a somewhat redundant optimisation given the tiny amount of data involved.
Glad to hear that the feature is used by people, though, as going backwards in time is not so straightforward.
Last day of working before two weeks off. It'll be a staycation mostly (we've both had a lot going on this year and we need some space to just be), but we might nip to France for a night to eat the food and stock up in a French hypermarche. On my shopping list: French washing-up liquid, which comes in lots of flavours that are way less boring than the Dutch ones, and a dozen of those glass jars of pates and rilletes that last forever. I'm hungry now.