Diagnosis
This is detergent or fabric softener residue, not lint. The WT7900HBA uses an impeller (wash plate) and high-pressure jets. Using too much detergent, or the wrong type, causes insufficient rinsing.
How to Fix It
Use only 1-2 tablespoons of High-Efficiency (HE) detergent. Never use non-HE detergent. Do not use liquid fabric softener in the dispenser; use dryer sheets instead. Run an empty Clean Tub cycle with hot water and 1 cup of white vinegar or a washing machine cleaner monthly.
If That Didn't Work
The issue may be water temperature. Cold water washes do not always dissolve detergent fully. For heavily soiled loads, use Warm or Hot water. Select the Extra Rinse option for every load to flush more residue.
Heads Up
The detergent dispenser drawer itself accumulates residue. Pull it out completely and wash it in warm, soapy water. Wipe the compartment clean. This is a weekly maintenance task.