i booted up CS2 and joined a DM game on Nuke, and i was getting an abysmal framerate, which was confusing me because the game had been running totally fine the previous day. i messed with my video settings a bit, switched from fullscreen to borderless windowed and back, but nothing worked. i quit that game and went to a practice match on Nuke and my framerate was totally fine, so i knew it wasn't the map or anything.
i then joined an online casual match on inferno, and the skybox map from Nuke followed me lol. after a couple of rounds i quit that game and booted a practice match on Dust2, and the Nuke skybox map followed me there too.
i quit the game after this and verified the integrity of my files, but it came up clean. no earthly idea what could have caused this.