To help in testing, you could use a jumper from the backbox power (BLK-RED) to the common (WHite) wire on the F (match) relay circuit card. That will power the Match number lights during the game, so you can see what the match score is going to be. Use a 10-point switch on the playfield to move the match to the number you want for the end of the game. Use a different player's 10 point scoring to move the match number for the player under test.

S76_matchJumper (resized).jpg

Yep, looks like the OR+WH broke off the common point of the circuit card for Player 2, can you re-solder it?

You have the solder and iron? What type of solder do you have?

This is what I generally use:
https://www.amazon.com/gp/product/B00068IJWC/ref=ppx_yo_dt_b_search_asin_title

You should reform the wire a little bit, pinch the individual strands closer together with some needle nose pliers and melt some solder onto the bare end of the wire.

Clean the solder bump on the circuit card with some alcohol and let dry.

Then hold the wire with the needle nose pliers against the solder bump and heat them both up, you shouldn't have to add any more solder. Once the wire and solder bump merge, withdraw the soldering iron and try hold the wire still until the solder solidifies (about 10-15 seconds).

Remove the needle nose pliers and after about 15 seconds more, test the connection by tugging on it gently.

This is a good first problem to have - it doesn't affect game play, you can take your time and gather up the right materials and tools, fix it at your leisure, verify the fix by testing, and gain the confidence that comes with debugging/fixing your first issue...