Some of the photos you upload arrive carrying a signed record of how they were made. That is increasingly the norm for images produced by AI tools, and it is the record that lets an image say for itself what it is, wherever it ends up.
When we take such a photo into a packshot we convert it to a single format first, and our own signature goes onto the result. The record that came with your file is meant to travel with it — named inside our signature as the source ours sits on top of, so the chain from the original tool to the finished packshot stays readable.
For photos that arrived as PNG files, that was not happening. PNG is what most AI image tools produce, and the conversion step was handing the original to the signing step under the wrong format name — so the record could not be read, and nothing could be carried forward. A check on our side caught the loss and stopped the upload rather than storing a packshot with the provenance quietly missing, which is why the symptom you saw was an upload that failed instead of a file that came back thinner than it went in.
Those uploads now go through, and the original marking arrives in the finished packshot alongside ours. Where a file's marking genuinely cannot be carried — a format the signing step has no reader for — the upload is still refused, but now it says which format it could not handle instead of reporting a generic failure.
The photos affected while this was happening have been put back through the conversion, so their packshots carry the provenance they arrived with. Nothing is required from you.