ON30 2-8-0 not running

[SP Ron]

Hello forum!  This is my first post here.

I've had an ON30 2-8-0 I bought about 8 years ago on Ebay brand new.  It has run perfectly most of the time.  I don't have room for a full size ON30 layout yet, so I bring this loco out once or twice a year and run it to keep it lubed and moving.  Once about 3 years ago it wouldn't budge or even light up.  I fiddled with the connection from loco to tender and it seemed to want to move.  I pushed the connectors in tighter and it ran perfectly for a good 15 minutes.  I packed it up and put it away.

Since then, life has happened and the loco has been in storage (climate controlled in my closet) due to a marriage and moving.  Today I brought it out and attempted to run it again.  There were no lights or movement.  I fiddled with those connectors again and got nothing.  The connectors seemed loose and floppy to me.  I noticed on one of the larger connectors under the cab there is a phillips head screw, so I tightened it.  No movement or lights. Nothing.  Are there known issues with these connectors or the DCC system Bachmann has chosen?  I'd rather not send this one in for repair as it has been discontinued and I don't want to incur the expense.  I've done several DCC installs in N scale, but this loco is much more complex.  Does anyone have experience or suggestions on where to look for trouble spots on this specific loco?  Yes, I opened the tender and poked around.  Nothing is visibly wrong with it.  Thanks!

SP Ron