I am having this exact same problem as of a few days ago.

I did the switch test. It says 01. The manual says:
01 = #2 Left of outhole
#1 Right of outhole

This switch to the right of the outhole seems to be the problem.
switch.JPG

While trying to adjust the switch, my leaf switch tool touched the metal arm/bracket on the playfield, and that fixed it temporarily.

As soon as I take the leaf switch tool off that bracket, the 01 code comes back.

Does this mean the switch is not grounded? Is the diode bad?

That is with the balls in. With the balls out it gives the 03 code which is outhole.

Ahhh, ok.
I took the balls out, and the test reads 0. So it tests fine. When the start button is pressed it registers 06, which is its corresponding switch

Yes, I was clueless, but now I understand!

Nice lineup!

I'm building my own. I'll be at three soon.

So my Vector is still occasionally, and randomly, spitting a ball into the shooter lane upon completion of any of the sets of drop targets.
The switch test still shows everything is in order.
On multiplayer games it does Not occur 100% of the time.
I'm not sure what this means. Maybe the game rom is slowly failing?

On a side note, pinsider DRD on the last post of page 1 of this thread provides some good thoughts on Vector. This game is challenging in a similar way to Flash Gordon. It's a total ass-kicker, and when it is set up nicely, it is a joy to play!

"Hit the showers!"