the 00-99 unit is on the other side of the lamps, so it's not a factor assuming only one lamp is on.

the only thing it can be is what howard said - wire 13-4 is shorted someplace. Often it's a bare wire stapled to the wood, so if all else fails, cut it between the 50 and 60 lamp and see which half has 6VAC when measuring to wire 30, then go from there.

if you cut the wire with sharp snips, the ends will butt and solder back together easily.

to clarify that ... the 13-4 wire only goes from the match adjust plug to one side of all the match lamps. The lamps are those circles with the 00-90 numbers in them.

the transformer has a hot and neutral side, one side of the lamp needs to attach to hot, the other side of the lamp to neutral.

in this case, wire 13-4 is essentially connecting one side of all the lamps to hot (via 23-1), and the 00-90 unit connects one lamp to neutral to light it.

when you pulled the match on-off adjust plug, you disconnected hot from all the lamps ... but one lamp still lit. The only way that's possible is if there's a short onto 13-4 (if you ignore the bizarre possibility of a path to hot thru another lamp ... and in that case two lamps would be dimly lit).

debugging via the schematic is generally a game of finding the load you want to power (load = lamp, coil, motor) and find a path from that load to hot and neutral.

there's usually lots of possible paths on one side of a load, so you find the path(s) that should be closed at the time you care about and determine why it's not working using inspection, voltmeter or jumper wires.