Unable to upload screenshots of in-app purchases

On App Store Connect, we're required to upload a screenshot of in-app purchase screens to submit them for approval. Unfortunately the uploader only seems to work about 5% of the time, with it failing (see screenshot) every other time. I've tried several different browsers and it's the same every time.

Can something please be done about this? It's not acceptable for the developer tooling to be this buggy, and it's preventing many people from being able to submit in-app purchases.