Dwarfen Fortress exp fail upon winning the map

[Redmark]

As the title says, the timer goes to 0, all lost souls are purged from the map, you're supposed to win the map, but we instead got a mission failed screen saying that one of the fire shamans died. I've completed the map once before on advanced, so is this an Expert diff only thing? We had a GM playing with us witness this also.
Please don't tie seasonal challenges to custom maps, unless they go through the same vouching process as the "official" maps 😕

[WindHunter]

One of your partners reported that he killed the Fire Shamans on accident when the game was ending, losing the map.