First step is see what tables cust is using and what wash cycle, Some cheap ones you have to use two tables and the longest wash to get a good result! The 500-in-one tables need long cycles too i’ve found but fairy ones seem ok whatever the prog. Other than that see the spray arms are in good order, could be stalling?
would suggest maybe a lack of water? That one has a filter that the customer never takes out to clean as the handle lifts off leaving the main filter still in place, could just be that.