I presume the MPU board has suffered battery corrosion in the past?

Does the problem occur when both J2 (playfield switch harness) and J3 (cabinet switch harness) are disconnected from the MPU board? (you can disconnect them live).

If yes:
Switch the machine off
Leave both J2 and J3 connectors disconnected from the MPU board
Grab your multi-meter and connect the black meter lead to ground.
Set the multi-meter to measure resistance, if your meter is not auto-ranging, set it to 200k ohms

With the red meter lead, measure the resistance on pins 1 to 5 on MPU J2 pin header. They should all read around 56k ohms.

With the red meter lead, measure the resistance on pins 8 to 15 on MPU J2 pin header They should all read around 56k ohms.

Report back any substantially lower readings and post clear pictures of the MPU board.

If the cabinet harness was still connected to the mpu when you tested, you can clip a leg off the capacitor on the tilt switch/plumb bob and see if that stops it.

Tilt can come from 3 possible switches in parallel with each other. In the cabinet there is the Plum bob and roll cage. There is an aditional tilt switch on the playfield. The switch on the door is slam not titlt.
Put the game in switch test take turns unplugging J2 and J3 from the mpu and see if either one clears the stuck switch. That will narrow down where the problem is.

If you don't have something leaning against the plumb-bob, it's high probability the tilt switch capacitor is bad.

If you disconnect J2 (playfield harness) from the MPU board and it still reports #07 (tilt) in switch test mode, how do you know the cabinet tilts are working? Did you also disconnect J3 (cabinet harness) to confirm the problem is on the MPU board?

While you’re under the hood, humor me and clip one leg of the capacitor on the plumb bob tilt. If it’s original that is likely the issue.

If it resolves the issue you don’t have to replace it but you can if you want.

This is really simple. Put the game in stuck switch test and unplug J2 and J3 from the MPU. If it still sows 07 stuck it's an MPU problem if not plug on J2 (playfield) and then J3 (cabinet). That will tell you if the short is on the playfield or in the cabinet.

See post #2 above.

There nothing worse than a poorly botched pinball machine.....

Yves

So I'm having this exact same issue on my Future Spa, but I unplugged J3 and it DID clear the stuck switch. What's the next course of action?

Checked the diodes, all have .4-.6 in only one direction, no switch contacts touching.

See post #3 and #5 above.
If disconnecting J3 from the MPU board cleared the tilt switch closure, then the next step is to cut one leg of the capacitor at the plumb bob tilt to disconnect the capacitor from circuit. The capacitor may have a partial internal short.

With the game off, reseat MPU J4 and the two connectors on the right side of the solenoid board.
Retest.
Still bad?
Very carefully swap U10 and U11 on MPU, using caution not to bend any chip legs underneath the chip.
Any change in behavior?

Of course, all of those connectors need to be rebuilt if they haven't been done recently.