Here
are a few items that might need updating:
P/N 675808 manifold. This solid one-piece rack mounted conduit replaces the multi-piece rubber tube and connectors that deliver the water to the upper spray arm. The original tube over time would deteriorate/collapse impeding the free flow water to the spray arm impacting upper rack washability
P/N WP3376846 upper wash arm seal. Can wear down leading to water pressure loss, again affecting cleaning
P/N 4172127 lower door seal. This flexible plastic strip replaces the original soft vinyl part that was prone to tearing that could lead to drips down the access panel
Now your machine may have these updates, either from manufacturing or previous service. In any event, if you need the parts they are inexpensive and simple to replace.
-LP