Hi there! [br]
I have a DS Lite too and sometimes when the game cartilage is faulty the screen would just freeze. Also, if it works when you press the bottom of the casing then it might be a defective motherboard. It might also be a misshaped casing which caused the battery to disconnect with the pins, so when you press the bottom of the casing it would reconnect again. Anyway, I think you should get a new battery and test things first. if you can't get one, try disconnecting the old battery and just use the charger and see if the problem is still there.