You are missing the prototype plastics with standoffs, no BSD, is complete without them. Also with all those GI LEDs all over the place, I cannot tell it the pop bumpers have proper colors installed and the factory plastics. Keep flipping.

After validating voltages from the WPC PDB and checking IDC connectors, it is time to multimeter logic probe test the GI triacs that control the lights.
It is possible you blew one out, it can happen due to the age of the component and voltage overload that might have sneaked by the fuse before it blew.
If your voltage from your test points and LED are still missing, you mostly likely still have a fuse issue (most likely).
If you did not test the installed fuses before you put them in the game, do it, fuses can look good but are not.
Checking the connectors eliminates others potential issues like connector BURN that were never corrected, but could exist on your machine including the pins, this is a contributor to electrical problems as well.

Always remember (beyond what you mentioned of your lesson learned), parts and electronics can fail at ANY TIME, even when nothing happened to initiate it.
If you are unsure of what I described, it may be time to get you feet wet in understanding basic electrical circuit theory of solid state component mounted electronics based on the type of machines you currently collect.
It is just part of the process of pinball collecting and learning.

Good video.

No offense, but that is not entirely true regarding the bats.
I have a BSD that was a HUO since 1993 which was bought NIB by the first owner with installed lightning flippers from the factory.
This was the original WMS "design intent specifications" from Oursler.
I picked it back in 2004, with verifiable sales receipts, and all factory materials.
Flipper assemblies are still original, based on construction and stamping.
The only thing that was added was the prototype slingshots with standoffs which I did myself.

It is possible this could have been an "operator option" because I cannot remember now, but this one was stock.
It is also possible that later in the production run, the bats were changed based on operator complaints, but the production really did not run that long.
They cranked this full production run of this game out in less than 5 months.
These things do happen, but manuals are not always accurate.

"Lightning flippers or bust" is my saying.

This gate is nearly the same thickness as a modern wire coat hanger. If you make your own, you can make it even stronger and the same shape. The only thing you will have to do is enlarge the gate joint holes. I did this for another collectors machine.

The metal composition in this case had no bearing on the functionality of "Mist Multi-ball".
Balls rolled past well, did not get "stuck", or interfere with the underside magnet mechanism.
It worked, and was cheap when parts were scarce.
If done, use NON-PLATE COATED coat hanger wire, to prevent "flaking".

It's magnetized...

Remove the glass and test play your game with your hands. Start all major feature sets. Listen closely. The only "whirring" functionality is the mist multiball motor assembly in operation and in reset mode (including game startup). It is possible the gearbox was slipping or the game did not think the ball was properly reset. It It does it again, you will know the cause.

Step 1: GI wire connection under playfield for cuts, colder solder joints or breaks, they are "daisy chained"
Step 2: GI bayonet socket oxidation corrosion and rust removal
Step 3: 5V test point on the PDB for proper specification range, may require rebuild
Step 4: IDC 0.156" connector and pins for burns, hacks, and loose wires.

It is one or all reasons.
Remember this game is over 20 years old.

Remove all game balls.
Go into diagnostics to the switch test menu.
Test all switches and watch for "double tapping" of multiple switches in a momentary "blip" status.

Install balls.
Test in "game mode", versus diagnostics, and test play the game manually with the glass off.
My guess is you have a flaky opto transmitter, or a momentary switch closure short.
This includes removing the castle plastic molding for visual inspection while playing, in concert with the ball trough.

Start simple.

When it comes to the "SP vs TAG vs LS vs DP" debate, the preference is SP DP, with some exceptions in late model games that do not carry the logo anyway, but for all intents and purposes are DP.

"Not all SP PFs are DP, but all DP are SP."

Conditions of environment are the critical factor in planking, along with how the PFs were handled during technical maintenance (cheater bars and torsion twisting), type of bulbs used for all different types of illumination, whether the game was left on all the time which causes fluncuation in heat cycles on the inserts, magnet use on the game such as the case of mist MB, cleanliness of the PF, and the number of plays that the PF has seen over the period of its lifecycle on the top clear coat.

BSD is notorious for planking for the above reasons mentioned regardless of PF manufacture type.

Heat.

"The best mod for BSD, is the simplest mod", prototype slingshots.
You just have to install the right kind and height of hex standoff spacers.
15 minutes, done.
I remember when original BSD proto slingshot plastics were obscenely priced ($100), when they finally ran out in stock, like 10+ years ago. Fortunately, a good set was reproduced with ink screening, and the color match is spot on.
Even the holes are drilled in the right places, unlike the some originals.
This is my third (and final) BSD, I purchased in 2004, an original HUO private home owner sale.
This is a "LS" playfield.

BSD_Prototype_Slingshots_(resized).jpg

There is no such thing in pinball.

Whatever magnetization problem you had will come back.
Mysteries are solved with deductive elimination of potential issues.