I think it likely yours is going through a phase and will return to enjoying crickets eventually. I have one picky eater who refuses to eat the same insect more than twice in a row.
If indeed your cham is just showing a preference, try to find other alternatives, as mealworms are not a great diet. I agree with CCrazy post - offer as much variety as possible: butterworms, silkworms, roaches, moths, etc (try not to offer waxworms very often - too fatty).
Is it possible the crickets are not as easy to see as the mealworms? Some chams are better hunters than others.
Another possibility is that a cricket has a negative association from a recent incident. Is it possible you offered a cricket that was too large recently that either bit your cham or had large hind jumping legs that may have got caught in its mouth?
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SandraChameleon@gmail.com
BC Canada