Ok, what you are seeing then is simple GI connector burn out. That is very common. It is cause by underdesign/overload of the GI bulbs circuits.

As you are now running LED that will not happen again.

If the connector is really burnt bad, you will want to replace that connector. From the pic it does not look bad at all.
If the connector is just mildly burnt, and your reseat of the connector cleared up the problem, you are done. No more testing/removing components or you may/will end up breaking something.

G,
All those transistors that "buzz" when you are testing continuity from ground to tab (sink) are indeed bad. They are shorted, not open - this means they are conducting all the time. Any device operated by those transistors is going to be stuck on when power is applied, if power and coil are good. In your case it is the left &right kicker, jet bumper, flasher 9 and 10, according to the transistor numbers you mentioned.

At this point what exactly are you trying to fix?

You had a flaky pop bumper that turned out to be a switch adjustment.
You proactively changed the zeners on the P/S to lower the display voltages.
You had a some GU out due to a connector issue that is all set.

Why are you randomly testing all of your transistors?
Do you have another problem that your trying to isolate that I am missing?

I'm lost.

Perhaps something is wrong with your test method/test equipment? Perhaps the wrong transistors are installed? Eliminate your DMM from the equation, all you need is an alligator clip lead. From the guide:

Testing TIP122/102 Transistor and Down-Stream Wiring/Coil.
If the coil fires in the above test, you may have a transistor problem. You can also test the TIP122/102 transistors this way. Only do this for the TIP122 or TIP102 transistors! Damage can occur if this test is done on other transistors (like TIP42 or TIP36). This test will test everything from the CPU board down to the coil itself. If the TIP122/102 and coil pass this test, and your coil still doesn't work in game play, you have a problem more "up stream". All that is left is the 2N4401 pre-driver transistor, and the logic TTL chip that ultimately controls the whole process (a 7402 for the special solenoids or 7408 for the standard solenoids).

Game is on, and in diagnostic mode (push the center red coin door button down, and press the black button closest to the coin door; this will put the game in diagnostics mode).
Remove the backglass.
Find the transistor that controls the coil and/or flasher in question (refer to the manual).
Attach an alligator clip to the grounding strap in the bottom of the backbox.
Momentarily touch the other lead of the alligator clip to the metal tab on the TIP122/102 transistor (only works on these).
The coil or flasher should fire.

Not being a bane. "but the game appears to work correctly" It's just very hard helping you fix something when I do not know what you are trying to fix.

It's all well and good trying to learn, but no where do I see what you are troubleshooting. It looks like your looking for problems on a running machine. Not a good way to learn.