I decided to try to "exercise" the system to (A) better document the problem and (B) see if the symptom improves.

It appears that the problem has "self-resolved" which is both good and bad news. Glad everything's working OK but sure wish I knew for sure what the problem was.

I manually raised and lowered the bus to the high and low limits, and then went to ride height from both extremes. Then resumed to ride height after just a little bit too high and a little bit too low. Then back to full travel at both extremes. Then the whole pattern all over again.

One interesting side note: I decided to take measurements as the bus was moving up and down. The front ride height returned to the same constant whether achieving ride height from either full up or full down position.

However, if I dropped down to road ride height after the bus was at the upper height limit, the rear returned to an elevation 1/2" higher than achieving road height by raising from the lowest position.

Of course, this was strictly a static test. I'm guessing that if I drove the bus any distance, the rear ride height would settle out to be the same either way as the ride height valves adjust up and down during travel.