You may have to replace those 4 switches. Typically you remove the diode and actuator from the old switch and reuse it. Be sure and connect the wires and diode exactly the same on the new switch.

Can't see why the ball would be stuck there. Maybe the pitch is too shallow.

Welcome to the wonderful world of pinball repair/maintenance!

STTNG has a feature where if a switch is not triggered in some number of games, it assumes the switch is broken and reports it on the tech report that you saw. Take the glass off, start a game, grab the ball off the playfield. Try manually triggering those switches with your finger or a ball. If they register, great! Forget about the error messages. If they don't register, report back and we can help you troubleshoot.

The fact that your game has 230V scratched out probably means it was originally sold overseas. Now that it is back in the USA, we call those re-imports. Look at the coin slots in the coin door and tell us what coin denomination is on the coin slots.

Can you post a picture of the main board modification you are referring to?

Keep in mind that if a switch hasn't been activated in 30 games it will show in the test report. Try activating those by hand then resetting the game to see if any clear. Could also be more than one problem. There could be a broken wire or two at other working switches not passing the row or column signal to the failing switch.

As far as the stuck ball, it looks like you have two stacked rubber rings on the left, and the lower one is sticking out from what I see in the pic. I think there is only supposed to be one ring there.

got some more pics of the game? interesting.

Some of those switches are probably optos, not physical switches

Some good advice on here, some horrible advice and horrible dart throwing before doing research (optos).

Those mentioning the switches not being triggered are correct. It could be as simple as activating the switches in question. See the attached image for their locations.

Open your coin door, there are four buttons. Press the button on the right a few times until you get to the menu. Use the second to right button to get to "Test" menu. Enter by hitting the right button. Select the first option "Switch Edge Test". Now activate the switches in question. You should hear a beep when it is activated and it will state the switch number on the screen. Once you activate all the switches in question then exit the menu by hitting the far left button several times. If you don't hear a beep when you activate the switch there is a problem with the switch. Look for broken wires, etc.

Switch matrix (resized).jpg

STTNG is a GREAT game. If you haven't done so, my advice would be to go through the diagnostics and test everything (all switches, all lamps, all flashers, all solenoids, all general illumination). Aside from the issues you see at startup, I'm guessing you'll find other minor issues. Make a list of the problems found and tackle them one-at-a-time. One thing I noticed in your photo, it looks like the connectors at J120 and J121 are hacked (and possibly slightly burnt), so I'm curious as to whether or not all of your general illumination is working.

While you're at it, plan to get those batteries off board, or use NVRAM.

As with any game, be sure to remove the balls before lifting the playfield. In this game, it's especially important because you can damage the subway if you don't. There is an option in the test menu (the last one, 16 I think) to remove the balls from the playfield. After selecting it, you'll have to close the coin door or manually activate the coin door switch in order for the game to release all the balls (6).