The support posts on all the decks were bowing to some degree. This played a part in it but what seemed to be a less obvious cause was the grading of the lots. The house I inspected was on a lot with a pretty steep grade along the right-hand side of the house where the deck is located. Attached are some pics of other things I saw which appear to indicated shifting and sliding grades and possibly inadequate compaction of the ground.

Pic #1 - electric meter box on front wall pulled loose on wall (this was mounted in an area where the grade began to slope on the right-hand side of the house)
Pic #2 - two underground drain lines along the right-hand side of the house were pulled down and away from the downspouts
Pic #3 - sealant line on the AC lines where they passed through the foundation wall indicates the condenser moved a couple inches down and away from the orginal mounting location
Pic #4 - deck support post on the inspected deck was not only bowed but also out of plumb and in a position that appears to be consistent with my thoughts of unstable and shifting ground

All the decks in the pictures appear to have varying lengths on the support posts but I think what is actually happening is the posts are sinking/moving as the grades shift and move.