Not sure why this was done has this has nothing to do with flippers or the drop down target.

Could be a mechanical issue, run through the drop target up down tests to see how it behaves.

For the most part there are only two switches in the game that are going to enable the second lock, they are the drop target and right orbit switches, I would focus my attention on these two switches. Keep in mind a bouncing orbit switch (possibly from vibrations) is going to be detected as multiple hits and enable the next lock as well as drop target for the next lock.

There really is a lot of potential here for a switch matrix issuer being behind this with the almost always closed Trough up opto and the drop target, shooter lane, and right orbit switch.

When you select the Lock mission the drop target will fall, this will cause switches 57, 67, and 68 all to be closed which is you have a switch matrix issue in this area could cause a phantom read on right orbit switch 58; an issue like this would result in the behavior you are seeing as the game would enable a lock as soon as a ball enters the shooter lane.

pasted_image (resized).png

If you wouldn't mind humoring me real quick try doing this:
Start a game, but dont select a mission, just open the coin door and go into switch test with the ball still in the shooter lane. then with your finger hit the drop target to make it fall and see if switch 58 registers. If nothing happens, raise the drop target from the test menu, go back into test and hit the right orbit switch to see if the drop target registers down; if this is happening then in game you would see the drop target coil attempt to raise the already raised drop target.

If you have a bad switch diode in the shooter lane you would see both of these things happen as switch 58 would cause a phantom closure of 57 and 57 would cause a phantom closure of 58.

EDIT: Dangit ...this didn't work how I thought it would, I put a jumper across the switch 68 matrix diode in my machine and the game didnt care until switch 57, 58, and 68 were all closed at the same time, I then got phantom closures of EVERY switch in column 5

Thanks for documenting the repair actions.

Just to add a tittle more info to this; I've actually seen this type of switch issue before but its usually caused by installing the clear plastic cover upside down and allowing the switch actuator to move to the side as this plastic is there to prevent what you are describing from happening. I actually cut about 1/2" off of the actuator arm that was on my machine (may not have been the original) as it was way too long and was hitting the spring.

I did replace the plastic with one that wasn't scratched before I installed the restored mech in my machine.
1122 (resized).JPG

Of that there is no doubt as you would not be able solder the wires to the switch without removing this plastic if it was upside down

There is one more piece of information I failed to mention ...

WARNING: Way more information than anyone ever needs or wants to know is listed below:

First I have no doubt that my drop target is no longer "as built" from the factory. Part of this is because the original Cherry DA3 switches are obsolete and very expensive if you can find them. The other part had to do with the restoration and testing of this sub assembly.

I do not buy switches that have actuator arms, I buy bare switches and use the actuator I have as the actuator is a solid piece of metal and should rarely fail, and in the rare cases that it does fail/break, it's usually because of a something that someone did to it.

When I installed the original actuator from the DA3 to the DB3 I put it on the same postilion (inner) as it was on the original switch, this is a high arc position that requires a lot of movement to close, it also resulted in the switch hitting the spring AND jumping over the drop targets switch tab as I did not have the switch guard installed yet; this turned out to be one of those "good to know" experiences.

I believe I know the theory behind the design as the switch would read closed UNLESS it was all the way up; but honestly I don't really understand why you would want this. The other issue here is this is only true if you have a DA3 switch installed as this switch has a taller pin actuator, the DB3 is shorter and will open if the drop target is part way up.

I changed this on my assembly, I moved the actuator arm to the outer mounting point resulting in a shorter movement between open and closed and adjusted the switch appropriately to only read closed when the drop target is actually down far enough for a ball to pass over it ... in theory, should my drop target spring break, the game will not try to fire the drop target down coil forever but will acknowledge it as a drop target switch failure before burning up the coil or blowing the drive transistor. With the drop target switch now adjusted in this manor the actuator arm was far longer than it ever needed to be and I cut the excess off to match the mechanical drawing of the assembly that was linked by Dellis in a previously post in this thread.

https://www.marcospecialties.com/pinball-parts/614-1234