Why doesn't gun move in space invaders, but fire button works?

When I try to play Space Invaders, the gun along the bottom does not move. The fire button fires missels ok. When the missils from the aliens hit the gun it does not destroy it. The missels from the gun destroy the aliens though. I've used a known good joystick and that's not the problem.I also went to the two player mode and the other joystick port don't move the gun either with different joysticks. Also, when playing Kaboom, with the paddles, the bombs keep coming and can be caught by moving and catching them ok, but this will continue until you miss and then they will hit the ground and it starts over again. If you continue to play, the score increases indefinetly. The bombs never speed up because you can never get to the next level. I have replaced the 40 pin RIOT chip and it made no difference. Whats weird is Asteroids works ok when it is played. I bought another Space Invaders cartridge and it does the same thing. Can you figure out what is going on here. Can game cartridges get bad from age? Missle Command will not even start. Although the graphics are there. Thanks, Dave