Have you checked the gap of the switch to make sure its not just vibration setting it off? Any disc capacitors on any of the fast close switches (pop bumpers, star rollovers, etc)?

1st ball trough diode looks like it may be the problem. Sometimes the diode itself isn't bad, but the legs get squished and can short out. Strictly from a view of the schematic, that switch would be the problem that would cause your scenario. You can test the theory by seeing if the problem goes away during 5 ball multiball (1st ball trough switch will be open so diode condition won't matter).

I don't think there should be a diode on the left flipper as the matrix only looks for the Right Flipper for the lane change.

You will want to check all of the switches in that column -> all 4 inline drops, right return and outlane and left outlane.

This is happening to my Centaur as well, Game starts, I hit flippers and 5K is scored even before launching a ball, I ran the switch test and #1 switch is not working correctly. Trying to figure out before MGC which is this weekend.
Any help would be greatly appreciated

Mine also won't go into 5 ball multi-ball

+1 on the 1st ball trough diode. It is shorted or is being shorted across.

EDIT: Doh...too slow!

It takes three closed switches, one with a shorted diode to cause a phantom switch closure elsewhere on the playfield. We really need to know which switch is scoring 5K to determine where the problem lies.

In your case the 1st inline drop target had to be down. That would not (should not) be the case at the start of a game. And I can't tell from pics of the playfield if other targets score 5K or just the in/out lanes.

Another question I forgot to ask...does it score 5K everytime you hit the flipper or just once and done?

I just looked at the schematics and in my machine. The schematics say both left and right and I confirmed I have lane change switches on both flippers. Each one has a diode.

If you have a lane change switch on the left flipper and it doesn't have a diode, you could get phantom switch closures if the flipper button is held in. That said, you will probably not experience any issues unless one of your coin switches gets stuck since there are no other playfield switches in the same matrix column as the lane change switch.

Banded end ties to the brown wire, non-banded end to the grey/yellow wire.

And I misspoke earlier about the lack of a diode probably not causing any issues. The flipper switch is not in the same column as the coin switches, it is in a column with other playfield switches. So for example, if the "S" target is down and you hit the ball up the right side and hit the Release target while holding the left flipper up it will score the "2" drop target if it's standing. But you would probably only notice if the tilt or slam tilt were one of the switches that could phantom on you. That's not possible in this case.

I was going off the schematic posted above and didn't see the left flipper listed. Sorry for the mis-info. Good catch.

Ya I didn't remember both switches having lane change. I had to go look.

The right flipper is correct. I believe the banded end would connect to the brown wire when the switch is closed. I misspoke by leaving out the switch.