Hello, it has certainly been a while. You have been keeping yourself busy from the looks of it. :)
To quote illusioncards from another post, "The hash (MD5 he believes) for [each uploaded] image is logged [in the database] and if anyone tries to [re-upload] an image with [the] same hash they get stopped".
To get around this issue, simply remake the card(s) that you're having trouble uploading and try again. It only needs to be a pixel different so the same pose is perfectly fine (I believe).