The dishwasher frequently leaves a fine grain residue at the base of
the upside-down cups on the top rack. I questioned if the impeller was
wearing out such that sufficient water pressure was not clearing the
cups of residue. It's time to pull the unit for inspection...
In the end, I did add sealant to the pump assembly so that high
pressure water can't leak from the pump assembly (leaving more water
flow for washing dishes). This did not resolve the issue. Knowing that
the unit was "as designed" I looked at different detergents and rinse
agents. Online research typically follows comments that the dishwasher
needs to be cleaned - NOT - though the "dishwasher cleaner" does a nice
job to "whiten" the interior a bit.
In the end, the most productive answer to the issue is to use a rinse
agent. On a rare occasion a slight bit of residue can be experienced.
While the rinse agent bottle can be a bit costly, the amount could
readily last a year or more - thus the cost per wash is trivial.