The rails are high-end ball bearing style but apparently wear out over time.
Ordered both right and left rails even though only one had worn out - figures the other would go soon and the incremental labor and $ was small.
Had to pull dishwasher out to access rack rail mounting screws that go from outside of tub to inside. Only took 20 or so minutes to
1. undo screws holding top of dishwasher in place to underside of counter
2.lower front leg adjusting legs so dishwasher could roll out
3. Roll out dishwasher
4. Remove top rack from rails following instructions in user guide
5. Replace rails via 4 bolts/screws holding rails in place on each side
6. Put dishwasher back in place and return legs and screws holding dishwasher in proper position
7. Put top rack back into rails
Works like new again!