1dx ..horizontal strip of light at top of images

Have a look at these. Know nothing about Canons, but found these quickly 2 on Google search:
https://www.canonrumors.com/forum/index.php?threads/1dx-mark-ii-shutter-shading.33680/
https://photography-on-the.net/forum/showthread.php?t=1385823 (click on the blue link within the 1st entry on page to get image below.) I rotated it to match your issue.

https://www.canonrumors.com/forum/index.php?threads/1dx-mark-ii-shutter-shading.33680/
https://photography-on-the.net/forum/showthread.php?t=1385823 (click on the blue link within the 1st entry on page to get image below.) I rotated it to match your issue.


It is almost certainly a shutter problem with one of the blades slowing down at the end of the travel. It would not matter at a low shutter speed but would become critical at high speeds. If it is the shutter, it would be the same whichever memory card you used. I am sure it could be repaired though.
Dave
Dave

Quote:It is almost certainly a shutter problem with one of the blades slowing down at the end of the travel. It would not matter at a low shutter speed but would become critical at high speeds. If it is the shutter, it would be the same whichever memory card you used. I am sure it could be repaired though.
Dave
Yep I thought it would be something to do with the shutter.. Ill get it sent to the repairers tomorrow let them check it out..