Hi there @irismanda!
Don here from Shopify.
The first thing I would always recommend in a situation like this would be to clear the cache on your current browser or try using a different browser to see if you can complete the form upload there.
I'd also ensure your browser is as up-to-date as possible, and to update it to the latest version if necessary.
Could you let us know if you're having an issue with uploading the image of the back of the document just, or if you also see this when uploading the front image of your ID doc?