When I try to delete "autism" from Deliverance's keyword list, my contribution keeps getting rejected.

I've tried to delete "autism" from the list of Deliverance's keywords four times, and each time I gave an edit reason. But each time, it got declined, because "We have been unable to verify your contribution." I don't know why this happens for this particular movie. I've deleted "autism" from other movies' keyword lists without any trouble. I've also added keywords to movies much more obscure than Deliverance without giving an edit reason, and they were still accepted. Does anyone know why this particular edit is such a problem?