It's my first post on this forum because I'm desperate for an advice. Here's my story.

-Bought an lg dishwasher LDF7920ST fully-integrated in may 2011. Had no trouble for 1 years
-Then motor started to do a whining noise, dishes start to get dirty (specially top rack). Seem like the DW was not filtering the dirt from the water.
-Went on internet (amazon,forum...) and tons of people had problem with the DW model. Most of the times 1/5 stars. Most of the people finally changed it after failed reparation.
-My mother-in-law finally convince me to call awful sears technical service. Service told me there was a defect with the PCB, motor and firmware. They would come in to change the defective part.
-Technician told me my installation was not right (drain going in the basement) and the reason for my problem was the syphoning effect because there was no water in the DW.
-Started arguing with the tech that there's water in the DW during pre-rince,clean,rince cycle. Have no error code, and the dishwasher was working perfectly well for 1 years.
-He finally left not changing anything because my installation is not >. Ask him to at least change the > (motor, pcb, firmware). He refused saying that my installation need to be right before.
-Called LG technical support, they refuse to service me because sears has exlusive repair right during and AFTER warranty.
-I don't feel like reinstalling completely my DW just to get my part repaired. I'm out of warranty june 18th 2013 and according to most people problem keep coming back.
-The tech gave me the explanation that the syphoning effect can be intermittent. How come it's intermittent when there's no problem for 1 years then problem non-stop for 6 month.

What should I do? Is the syphoning effect really the problem when there's still plenty of water in the DW during cleaning AND had no problem for 1 years? Problem is happening all the times and not intermittent like he said?