Kitchenaid undercounter ice maker

This ice maker just stops making ice, although water continues to run and run. Repair guy first replaced thermister, worked for awhile then had to replace pump.

Has stopped making ice again. Cleaned it twice. Repair guy says it is the evaporator. Says it may be "pitted" and therefore, ice does not slide onto grid. This keeps water running. Any ideas? Repair guy is very costly, $400-$500. Will order the part myself, if this sounds right.