Need help with Selection Box

My Selection Box works okay on the A Cards but when I go to use the Geometric Cards I have problems. I get the Card setup then when I go to do the quick downward push of the Card Advance switch it doesn’t do the quick move as it should to make sure the pattern is lined up…it keeps going. On the rare occasion that it does stop right away (once) when you then hit the button up it then keeps going in the other direction instead of stopping & beeping. It never lets me setup to knit the Geometric Cards. Any ideas what might be going on? I’m fairly comfortable opening the box but need to know what to look for or what to do. I can follow directions if told what to do. Any Help or ideas would be greatly appreciated.
Thanks for any and all help,
Mary Jo