Don't know how an original Gottlieb was wired, but when my Williams was doing the same type of thing, it was the flipper control board. I would test the transistors on the board, you may have one or more bad ones. If it is the board and you don't know how to do board work, I would see if Rottendog makes a replacement or send it to someone who knows how. Here's a link on how to troubleshoot and test
http://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Transistor.2C_Silicon_Controlled_Rectifier_.28SCR.29_or_Field_Effect_Transistor_.28FET.29