I’ve got the same behaviour too on an iPad pro, 13 inches with iPadOS 13.1 .
This seems to apply to all cloning / pasting tools, including the healing brush, the clone tool and the patch tool.
I believe the issue Twtw and me have is a lack of the `force pixel alignment` option for those tools on the ipad app (or it is well-hidden enough that I could not find it).
(See link for a discussion for the desktop app).
Could this function be added to the app?
For certain editing tasks like greyscale-images with patterns this is a huge drawback compared to apps with pixel-perfect copy-pasting.