My cham used to do this. I notice that mine does it when he's really not that hungry but just wants a quick bite of something to snack on, but doesn't want the full meal…if that makes sense.
In the case of your cham, maybe it's the same thing, or maybe it just needs to get used to eating a feeder that struggles a lot…sometimes this can intimidate a cham, but it'll get used to it.
I bought superworms for my Rudis Chameleons... but they look so big. Will Trioceros Sternfeldi really eat superworms or are they too big for them? They now eat crickets (sm-med), mealworms and wax worms.