Credited twice in two different departments, I only needed the one (double credited)

I have a role that was credited twice, but one in Visual Effects Department and the other in the Animation Department. I wanted to only keep the credit on the Visual Effects only (as that's more accurate), but every time I try to delete the credit in the Animation department it would get rejected. I even added explanation as being "double credited". Not sure how to address this as I thought I was following the right approach in correcting this. Any ideas as to how I can get this fixed?