Agreed, likely the Q3 transistor is shorted which caused R16 to blow out. Grab some spare transistors while you're buying parts: "TIP102" NPN darlington transistors.
Those resistors blew for a reason. Transistor Q3 drives the knocker coil in the cabinet that doesn't have a proper fuse. Check if that coil is shorted.

A power supply issue would have caused many more transistor/resistor failures.
The knocker coil has had a short circuit that then caused the Q3 transistor to fail and short circuit. This put a high voltage/current through resistor R16 that caused it to burn out.
You need to do some investigation around the knocker coil in the lower right side of cabinet. Make sure the coil has a diode on it and the diode is correctly orientated. Feel free to post some pictures of that coil. That coil should measure around 11 ohms resistance from memory.

Oh, PinWiki is a great resource if you haven't come across it - it lists the test point voltages.
https://www.pinwiki.com/wiki/index.php?title=Bally/Stern

The primary feature of diodes is that they conduct current in one direction but act like an open circuit in the opposite direction.
If you have a new diode out of circuit, set your multi-meter to diode mode which looks something like this: ---|<|---
Place the meter leads on each diode leg.
With the meter leads one way you'll get a reading around 0.6V or 600mV depending on your meter readout.
If you swap the meter leads around, you should get no meter reading change.

Resistor are non-directional - either way is ok.
Diodes on the other hand are directional, one end of the body usually has a band of color around it.

I haven't experienced those particular ones go bad, they're usually rated for high voltage. You can check if it's short circuited with your multi-meter.

Missing the last MPU board LED flash usually means the 5 amp fuse at F4 on the rectifier board in the lower cabinet is blown.

Are you referring to the replacement BR1 bridge rectifier job? It's not great - they used a bridge rectifier with lug connections instead of through hole leg connections.

My concern is the burn mark under the long white ceramic resistor, that's not normal. You should unsolder one of the legs of that resistor, bend it up and look at what's going on.

BTW, fuse F4 looks blown to me.

Yes, but I don't suspect it's bad. If it measures 600 ohms it should be ok. Lift it off the board and see what's going on.

That's for the missing centre coin chute switch. Just tape it up so it can't touch anything.