I purchased a 6 month old D3121 from a bankrupt business. Someone really intelligent put powdered detergent in the liquid rinse agent compartment. It has become solid. I have picked out the majority of it with a toothpick and used a can of compressed air (computer keyboard cleaner). Can you give me the best way to get the remaining residue out? A light soap film is still on my dishes. White vinegar maybe? All help greatly appreciated.