Did they really loose their names? or it just meant that they "became" butcherable?
They keep their names, but become cageable/butcherable once again.
I actually think I figured out why none of my instruments were ever played over the course of 15 years. Somehow, a large number of my instruments managed to get "locked" somehow, yet were still tasked for playing. I was renovating my tavern (deconstructing everything, including the flooring, to get rid of blood and vomit), and there were some instruments that outright could not be moved in any way short of DFHack. The moment I used autodump to destroy them, I started seeing the remaining instruments get played or simulated.
I'm also getting all kinds of strange bugs now in pathing and occupancy, including such things as constructions randomly forgetting what material they were made of (Stoneware Block Pillar becomes _Pillar and turns the color of a soil tile) and spawning a sand floor up in the air on deconstruction, completely empty tiles becoming unpathable and unbuildable, dwarves becoming stuck and dehydrating to death in the middle of completely open ground, fluids refusing to flow, and all sorts of other craziness.
Oh, and as for an actual trivial finding, visitors seeking to petition will cheerfully path to your mayor... even if said mayor happens to be riding a minecart through 7/7 water at the time. End result: one half-drowned mayor, one derailed minecart, one badger man corpse, and assorted bits of clothing floating in my automated swimming pool. Draining and refilling it to retrieve the bodies is going to be such a pain...