Having the same problem and this is very frustrating.
My content-type is either image/jpeg or image/png depending on whether the image is taken on the compuer (in browser, testing) or on the phone.
I am sending the proper base64 encoded string as the data and on the computer everything works fine. This is using the imageInput component and it works whether its a camera photo or an image uploaded to the component.
On mobile, the upload is created, the metadata for the file shows jpg or png but the base64 string comes up instead of an image. For example:
This is a big problem for my company that requires a fast solution by retool.
Thank you for your prompt attention!