how to repair kitchenaid kud523oyo model leaving particles on top rack item?

My superba model kud523oy (probably 12 years old!) is leaving particles on the glasses - top rack- and some on the bottom plates. I always find particles of some sort on the bottom indent of the glasses placed on the top rack upside down. This even can happen if they are on the bottom rack.

Use Cascade powder with additional rinse aid either Cascade brand or jet-dry. Water is hot - seems like it takes a long time to heat up, but this is probably due to older design.

Husband is handy man of the house and we seldom have reapir folks - I think 5 in 34 years!!

Thanks for help. I will monitor the run tomorrow night to see if water level is at/near heating element, arms are spinning. Oh, how does one clean out the upper arm on the inside?

Martha