Indicator does not change in real time as I shift. Stalls, then shows correct gear.
It just started this, 20k miles.

Looks easy to get to/take off. Is it something to clean/wipe off to get it back to normal?

I have noticed mine sometimes has a little lag. Maybe just a second or less burt i have noticed it not changing exactly when the shift happens.

+1, Mine lags a second or 2 some times. 06

Could you share a bit more? What did you take off and clean?

This here thing below my finger tips? With the white styrofoam circle?

Does the GPS set a code? No.
Does the GPS set the gear eventually? Yes.
Do I have a problem? No.

Is my dash the last to see it? Yes.
Is my dash on a pulse train kind of, 'not priority' you have to see the number immediately? Correct.
Is my dash going on the blink? No.

Should I assume a resistance somewhere? Hard to say if no code and the number pops up seconds behind.
Should I assume it's internal in the GPS and hard to remove the 'Mag-factor' inside and those touch points? Yes.
Should I look at my GPS connector prongs and look for green corrosion having some resistance factor happening? Yes.
Should I always remember magnetism = creates heat, causes a chemical [resistance] reaction, makes electricity? Yes.

I keep my shit clean as shit!

Stupid bike. This weekend I saw it get confused and think I down shifted from 5th to 4th before it realized I had shifted to 6th.

You just need to convert to GP shift and that will solve the problem.