23 is supposed to be connected to 22 and 24.

It is part of a big clump of ground connections.

It all looks normal.

Hacks try to "reflow" the solder on the pins with too small of an iron.

Because all those pins act as a heat sink when bunched together, someone probably got out a Solder Gun, lol

An oxidized connector with a lot of current running through it can heat up.

It does not mean that there was a short, just high resistance.

That looks like P23 and P24 burned? Those are not the typical pin(s) to burn on that plug. P23/24 is the ground return for the solenoids. I'd imagine that connector passed tons of current to burn like that. The ground return for the solenoid shouldn't burn up like that. The fuse should blow. Check the rectifier board for the correct value at (F4 i think it is) and then check the solenoid fuse for PF. Check the flipper relay, are there any traces burnt off around the flipper relay? Any solenoid coils melted like a flipper or knocker? Id assume a solenoid shorted, started consuming tons of current, the fuse didnt blow because a bonehead put a 20amp fuse in there, and the connector there started to be the weak point that burned open.

Get a new connector housing, new crimp pins, and new header pins. I am not sure if anyone makes the housing new anymore, so may end up super gluing too smaller ones together or stealing one from another game

For what it is worth.... bally went back and forth isolating the solenoid ground return from the rest of them on the driver board j3. Earliest boards are commoned together at the driver board. Early 80s isolated back to rectifier, then later on they commoned to the other grounds again at j3. They where probably trying to get rid of the extra noise that leaks into the switch matrix. From your picture it looks like the grounds are all connected together, but might not be.