After having pushed my site live (after having a lot of fun in figuring out how Automad templating works), Bing search console mentioned missing "alt" attribute with the images. I am using the "caption" part of the image to set in the alt attribute. I went in the interface and added a value for caption containing a ". Due to that, the images turned out not to be editable anymore. You just get the fields "Filename" and "Caption", without an example of the image, and both fields empty. Saving also results in an error.
I wasn't sure if you wanted me to report it here or on Github, so let me know if you want me to move it there. I guess a simple solution is to either present the user with an error that the " aren't a viable character, or maybe change the " to a '. Or maybe it's a different bug that just needs fixing 🙂
For those people affected by this, just go the folder with the images on your browser (should be in the "pages" directory), rename the .caption files to .txt, change the text, and revert it back to .caption files (or overwrite those files with a corrected version). That resolves the problem.