soap sispenser opens intermittently

I have a kenmore ultra wash portable dishwasher and the soap dispenser will only open intermittenly. I have taken it apart and moved all the parts manually and they seem to be working fine. I also got a new cam and follower part and installed them and that did not do anything to help. What could the problem be? I am at a loss as to why it works by hand and when I run the dishwasher most of the time it will not open. Also I know it is not getting blocked be any dishes as I have made sure there is nothing is the way.

Thanks for you help!
Wade