There's a strap on the camera but I'm quite sure it wasn't in the way.
The "lens hood" is more like this setup, with an ND filter on it. It's so I can use my 77mm ND filter with a 52mm thread lens.
I have some images with vignetting and it occurs around the edges. This I notice and can pretty easily diagnose. However, this is different.
I'm beginning to think that maybe it does have to do with the camera body itself. I've been testing on a Nikon D40 with the lens and ND filter and haven't had any issues creep up. Will definitely shoot more test images but would like to see if there's any more suggestions.
Kinda sucks this happened during a wedding. Thankfully, it was 1 of 3 cameras.