Diagnosis
That's a misaligned door or a worn gasket (the rubber seal). Over time, doors can sag on their hinges, or the gasket can get torn or stiff and not make full contact.
How to Fix It
Start with alignment. 1) Open both doors fully. Look at the hinge mechanism at the top of the problem door. You'll see a hex-head (Allen) bolt under a plastic cap. Loosen this bolt just a bit – don't remove it. 2) Now you can gently lift or lower that corner of the door to close the gap. Have someone help you hold it in the perfect position where the door sits flush with the cabinet and the other door. 3) Tighten the hinge bolt back down firmly. Test the seal by closing the door on a dollar bill – you should feel resistance when you pull it out.
If That Didn't Work
If the door is aligned but the gap persists, the gasket is the issue. Inspect it closely for cracks, tears, or a permanent crease. You can try cleaning it with warm, soapy water and massaging it back into shape, but if it's damaged, it needs replacement.
Heads Up
When adjusting the door, make small moves. A tiny adjustment at the hinge makes a big difference at the bottom of the door. And if you replace the gasket, warm it up in hot water before installation – it makes it much more flexible and easier to get onto the door panel.