Whenever I export JPG or even TIFF from Photos with full size, (45mp from Nikon Z7), and I load the photos into instagram, they show up as corrupted in the same way. The bottom of the photo has jiggly lines. It has nothing to do with the Photos library. I have repaired it several times and it happens even with my newest imported photos. So basically I cannot export my photos correctly without corruption in Catalina. I try various other sizes and compression modes until I get a clean output.
Also the corruption does not show until I load the photo into Instagram.
Also the corruption does not show until I load the photo into Instagram.