Help needed - air fryer

Without being flippant; "what goes in must come out". Try sliding a thin stiff cutting mat into the top of the basket.

How about expanding the outside "container" by warming it up? Either in the sunshine or evenly blowing warm air on it with a blow dryer.  

Next time when putting it away, slip a slim long piece of paper between the two.  Can be the outside  was warm when stacking and created a vacuum between them for a tight fit.  Heat up the outside not the inside.