I am having an issue of indexing my sites's images so frequently and finding no-follow tags on those images. Don't have any idea where Google crawler is finding those no-follow tags from. But my Search Console's coverage tab is burning with 140 errors! And all of those errors are from image urls. I guess this is a Bug which is hunting a lot of users.
No clue how to solve your problem, but problems like this ALWAYS happen whenever people reinvent the wheel instead of improving the wheel. Google recently fixed their webmaster tools WHICH WERE NOT BROKEN. Instead of IMPROVING a WORKING tool, they discontinued a WORKING tool and replaced it with a BROKEN basically USELESS tool. ONLY stupid people fix things that are NOT BROKEN. Wish I were rich enough where I could spend HUNDREDS of THOUSANDS of dollars to build a WORKING tool, then later throw it in the TRASH, and spend HUNDREDS of THOUSANDS of dollars to start all over again, and again, and again, ad infinitum.