Cannot rescale image once it's be "fusionized"

I have some 4kDCI clips in a UHD timeline. Which are all scaled up a fraction to conform.
I want to do some advanced tracking for stabilization in fusion, but when I come back to the edit tab, the clip has black bars at the top and bottom. But is in fact zoomed in. It's like Fusion stubbornly pumps out the original clips aspect ratio to the timeline even though the timeline is UHD, and will not allow you to zoom it up to UHD.