Basically I was switching between saves across worlds, one with “dark days of the dead” on (call it “classic”) and the one without (call it “default”).
I was playing “default” and killed some zeds without smashing them, saved it and in the main screen loaded a game from “classic”. Futzed around and switched back to “default”. Back in the game, I killed more zeds and then discovered that I couldn’t smash the corpses - they weren’t highlighted in the V screen, and my tile set didn’t indicate corpses to smash, even the ones from before the load.
I then saved the games and restarted the program entirely. On load, “default” was back to its smashing glory. Kinda weird.