Erratic Battery Gauge Readings on 2002 e825

When I am driving the gauge will suddenly drop 20%, car runs fine. When it did it this morning I slowed down and switched the ignition off and on several times. Each time I did it the reading came up, eventually coming up to where it should be. Could this indicate a problem with the big solenoid? Car seems to run fine, no connections seem to be heating up.

Both of our pre-2005 GEMs do this. The gauges are really just an estimate. I don’t see any way the charge indicator is related to the main contactor.