I'm not much of an RPGer, but since everything I've ever heard about Chrono Trigger is 'you must play it, best game ever, want to see my chrono fanart,' I thought I'd give it a shot. Problem is, the game locks up during battles. I can run around and yap at people, play games, etc. Everything seems normal until I fight some robotic cat or beetles, then the characters stop moving and all menus disappear. Music continues, pause works, and I can flip the menu bar from top to bottom, but nothing else.

Some cart information, which may or may not be helpful:
-The saved game screen has two slots for new games, the third slot is titled 'What Lies Beyond?' (Time 10:32, Save #36)
-New Game and New Game + are both available when starting. Previous owner beat the game and I can start anew with all items -- tried it for kicks and got the same freeze.
-Happens during both Active and Wait battle modes when a new game is started.
-Also happens during previously mentioned saved game.
-Soft reset works after the lock takes over.

Is this a common problem with these old Square carts? I can't imagine its the battery, as it still holds a saved game. The only other thing I can think of is erasing everything on the cart and starting completely fresh, but I'm not sure that's the solution to my problem, either. Any help would be appreciated, any wacky scenario suggestions (name every character a vulgarity!) will be attempted. Thanks.

I will also accept 'Go play Shadowrun' as a comedy answer, but only once.