PDF gradient adding extra color when opened Illustrator

Hello,

I've started to experience an issue with some PDF files with gradients in them that look fine in Acrobat, Photoshop, and other image viewing software, but look completely different in Illustrator. When opened in Illustrator, the gradient has solid blocks of color instead of gentle shifts to color. I figured out that the gradient is adding another dot of color on the slider that's in the exact same spot of the color in the middle. The coor dot it adds is the same color value as the dot to the left of it. I didn't create the art file. It's from a customer that was uploaded through our site. I thought it was some weird setting the customer added to their file that I don't know about but I had another file come in today that is doing the exact same thing with the gradient. It's a gradient with more colors but it's the same issue. All the dots on the gradient slider have a new one added directly behind them that are the same color value as the dot that;s to the left. Has anyone else seen this issue before?