wierd electrical cluster problem 98 Voyager

My 98 Grand has 190,000 kilometres (120,000 miles), runs great, but has
developed a strange problem in the last few months. The instrument cluster
goes dead at various times. The cluster lights work, and the warning and
signal lights above the cluster still work, but the gauges just stop
working. When this happens the "service engine soon" light also comes on. It
doesn't seem to depend on temperature or humidity, or how often it's being
driven. It sometimes changes while I'm driving, but usually when first
turning on the key.

The fuse and fuse holder check out OK. I pulled the cluster and checked the
plug and the ground and they're fine. I can't see any damage on the cluster,
and the circuit board is clean. There's no codes with the service engine
light.

OK now for the really weird part. I tried it today and the gauges were
working. Just for fun I pulled the instrument fuse (number 2, 10 amp) while
the ignition was on. The gauges stayed on! When I turned off the ignition
they went off. I turned on the ignition with the fuse out and the gauges
were off, as you'd expect, put the fuse back in and they came on, but then I
pulled the fuse again and once more they stayed on.

How can the gauges be working with no fuse? Is this proof of a bad circuit
board? Or maybe just some hidden dirt? Those clusters are expensive and a
pain to get at, so I'm reluctant to buy a new cluster on spec.