Diagnosis
The rubber door gasket (bellows) is probably torn or has a foreign object lodged in it, breaking the seal. On older machines, the gasket just gets brittle and fails.
How to Fix It
Unplug the machine. Inspect the entire circumference of the black rubber bellows. Run your fingers along the inner and outer folds. Look for cracks, tears, or hard objects (like a kid's toy or a bra underwire) poking through. If you find an object, carefully pull it out. If you find a tear, the gasket needs to be replaced—it's a common part for this model.
If That Didn't Work
If the gasket looks intact, the door latch or hinge might be misaligned. Check if the door is sagging or if it doesn't pull firmly closed. The strike plate on the door can sometimes be adjusted, but more often, if the door isn't pulling the gasket tight, the lock mechanism itself is faulty.
Heads Up
After any repair to the door seal, always run a short empty cycle (like a Rinse+Spin) to check for leaks before loading clothes. And to prolong the new gasket's life, leave the door and detergent drawer slightly ajar after use to let it dry out and prevent mold.