Upload stuck in processing

I didn't notice that someone else was already uploading pixiv #50867709, so I went ahead and tried to upload it myself (upload #703533) and it's been stuck processing for the last 17 minutes. Is there any way to cancel?

Never mind, after 2 hours it recognized it as a duplicate

Albert, in issue #2409:

Processing these manually seems to work. I wonder if it's a factor of the size.