Great news .
Re getting better as you play it .. yes that is normal , the switch contacts are designed to be self cleaning (thats the theory anyway) so once you sort out the last gremlins and play the machine  regularly it should be sweet.
You will find the occassional wire comes off.. its due to vibration .
Not sure if you know, but the schematic is supposed to represent the state of every switch after the start button has been pressed and machine has completed the reset cycle.

I also strip and clean all score reels and all other mechanical assemblies .. makes the game play better and also increases reliability .
Most of these games have likely never had that done since they left the factory.