So, after 4 years of no problems an issue has suddenly popped up in my human town. Suddenly my masons are refusing to use the brick splitting blocks. Even if I break them down and rebuild them, or make a new one elsewhere, everyone has just stopped using it. All my other workshops are still functional, even my masons shops can make blocks just fine.
After a bit of testing I've found out that the problem persists if I move my save to a new download of masterwork, and it also persists if I use one of the backup saves, even from before the problem existed, although not if I use a new world made in a new download of masterwork. I've not tried a new world in the old version of masterwork, as df crashes when I try to make a new world, not quite sure what's up with that, might be related.
Pretty much the only thing I can think of that might be related is that I recently did a civ alert to restrict everyone to a burrow for a few weeks. Although I don't know if that is connected at all, but it's the only thing different I've done recently (I did it in winter and only noticed the brick splitting blocks not working in spring, so who knows...)
I'm not totally sure if this is the right place for it. But I'm just hopeing someone might have a clue as to my issue. It's not a game ending bug, since I could just use masons shops, but it will certainly cost me tens of thousands of more stones over the course of the game if I don't find a way to fix it.