Thanks John, I tried the leaf switch with a business card but the issue persists.  Since it was working initially and the wires are soldered directly to the pins I think I'm going to replace the header pins and add a connector like you did in one of your recent videos.  Not sure where to get the connectors yet but I'll pull the cabinet out this weekend and see if I can find what type of connector to order.  I'll post pictures once I open it up again and maybe it will be more helpful.  I've been busy finishing a bar-top RetroPie cabinet.  Turned out nicely.  I'll add some pictures of it as well.

On a side-note, I was having some difficulties with a blue tint on the monitor.  I re-flowed the solder on the neck board and it's looking pretty good now.  Still needs a little color adjustment but much better than it was.

I recently purchased an original 1980 Defender cabinet off of Facebook (market place).  It's the first original cabinet I've purchased.  Brought it home and worked reasonably well for about a week.  

However, now when I move up on the joystick it doesn't respond (down moves the ship down, and all other buttons except the fire button are on-target).  When I press the Fire button (and hold it down) it shoots once and then the ship moves up or it briefly moves up and fires at the same time when pressing the fire button repeatedly.  I checked the connections on the control panel and don't see any obvious shorted wires.  Not sure, but I'm thinking it's the I/O control board (the pins are soldered directly to the board - yikes!).  Since this is my first original arcade machine purchase, not sure how to debug the issue.  I'm quite comfortable soldering, removing stuff, discharging the monitor, etc.  Any recommendations would be appreciated as I don't have any contacts in my area that have a clue about this topic.