I take photos on my Canon (It happens on both my Canon EOS Rebel t1i and my Canon EOS R) camera then download them onto my iPhone. Then when I zoom in close enough, there are these invisible lines on the image (when you follow them along they form a 3x3 grid on the image).This happens in every single image that I download from my camera to my iPhone. What are they, and if possible, how can I fix them?
Uncropped:
Half-Way Zoomed In:
Fully Zoomed-In: