I would put the game in switch test mode and verify all the switches - especially the optos - are registering correctly.

A bad or dirty opto switch could cause this behavior.

Start with the trough first. If the game thinks the ball count is off...it tosses a ball.
faz

Almost always a ball trough error. Well known issue with IJ, STTNG, (the wide bodies) etc. I spent several years re soldering resistors on the transmitter board until I bought the upgraded board set with the transmitter board that has resistor chips instead of the 2watt resistors that constantly break due to vibration. Best $60 I ever spent on a pin. Put those on over a year ago and have never had another issue.

I've done the same. No more issues. Ed

If not the trough I would do as you mention here and dig into the idol locks or subway optos.
All of them can get the game confused on how many balls and where they are located.
If it is the subway you would likely get a lot of "you cheat doctor jones" randomly as it would see the switch hit intermittently and at times the drop targets are in up position.
Check trough for divots and insure all optos working. Also see if you have the old style trough board or the newer style with gromets. The gromets really help with vibration issues.

GLM makes some good boards.

I have not experienced the find the stones ball end issue that you describe. Does it happen everytime or just random and happend to be at the end of a mode? If everytime when the timer reaches zero I have never seen this.
If intermittent it is likely opto or trough swtich.

Here is where I would start troubleshooting and asking myself the following:

For the idol lock, you should test all of your optos in switch test to see if they are all responding appropriately. When is the last time they were cleaned? Has this problem happened only once or multiple times? If multiple, can I manually reproduce the problem to show itself? You might have some bleed over light from the main light board tricking the optos into some weird behavior.

For the "Germany" switch, start simple and make sure the left outlane switch is gapped correctly and the wires are close to touching anything, then start asking yourself the same questions. Is it triggered at random, or when "x,y,z" happens.. That will help narrow down your search.

For the POA (more like POS, amirite?), First check that your playfield is level left to right. Check up top by the rollover lanes and check at the bottom by the flippers.

Check that the ball is resting against the stop-pin and the front wall of the bridge. The mechanism works by stopping the ball, letting it 'lean' forward, and just fall into the path. Too much (or any) forward momentum and it will go right past the opening.

Check that the pin can drop freely, without any resistance.

The two metal tabs leading into the POA need to be angled just right to let the ball in. This is more of an art than a science. I'll stress here that only TINY adjustments are necessary. Tiny.

How long does the path move? Indefinitely? Until you hit another target on the playfield? I would think it would still move until you hit something else, because you haven't hit any switches on the path yet. For all the game knows, your ball is sitting up there between the first two switches just hanging out.

Start slow, one problem at a time, and keep telling yourself, "fixing them is half the fun!" Eventually you'll believe it.

Good luck.

Those switches are all on the same rows. 6 and 8. Check to see that none of the switches are bent around the lugs. Sounds like a switch on each row was bent below the playfield and is shorting out.

I'd check switch 16 and 18 to make sure there isn't a short below the playfield and that the diodes look good.

I don't have a manual in front of me, but.........

If any of the POA switches are on the same row as any of the switches you mentioned, check them too, especially look for smashed diodes. Mine had all sorts of random switches activating, because a diode from the POA was smashed onto the switch. They take a pretty good beating from the ball hitting the START MODE saucer.

Diodes broken off switches also can confuse the switch matrix.