Masking not working on children of an image that masking is working on

So I'm working on a tool and in it, you're able to scroll around an image. If the image is oversized, that's ok, the masking is woking on the image itself. However, I have a feature where you can add a plane overlay to the object, becoming a child of the image so it scrolls and gets bigger/smaller with it. However, the masking doesn't work on the generated planes, and I can't figure out why. I've tried adding more masks to other parts, changing the hierarchy, but it's not quite working and I can't figure out why. I've attached the screenshot of what I mean by it not being affected by the mask; you can clearly see the red plane shape going past where the map image part is showing. Any ideas?