You very likely have a cold solder joint on the large PC board.
You have one photo looking down on a TIP-50 from the top side of the board, and I can see the legs of the TIP50's going into the through holes on the PC board, but there isn't any solder between them.
This would mean that none of those solder joints have been heated long enough, and I would pull that whole board and reheat every joint.
The red B+ wires are all connected together on the board, so there's no need to worry about accidentally shorting them together.
-PB