I had a customer that had the same problem. What I found was the internal seals on the top part of the sump assembly have blown out causing a reduced water pressure problem. You will need to change the sump assembly to resolve this issue. The part number is AJH31248604.
<<<What I found was the internal seals on the top part of the sump assembly have blown out causing a reduced water pressure problem.>>>
I've replaced hundreds of SUMP ASSYS---and have disassembled most of them. Never once did I see evidence of "blown gasket(s)".
I *have* seen SUMP ASSYS that were disassembled/reassembled by the *customer*---and the gasket(s) were unable to be properly reused (stretched/broken).
You say that you're a "specialist" on LG/Samsung appliances?
I'll then assume that you are an Authorized Servicer as well.
For the *6920* LG dishwasher go to LGs website and read the SERVICE CAMPAIGN which covers (10) different models of LG dishwashers. The SERIAL NUMBER becomes an important piece of information.
Also---relating the *6920* specifically---see:
SERVICE BULLETIN: IDSW20110150 (Guide Assy)
SERVICE BULLETIN: IDSW20100135 (Filter Assy)