No idea if this is applicable to you, but just in case it helps anybody in the future I had the same error message (though on an Options page with a textarea field) and it turned out to be unrelated to my fields at all, but because I had a deleted ACF Field Group in the trash. It was a duplicated and renamed group from an ACF import. Anyway, I emptied the Field Group trash and the error went away and my page fields worked again.
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