When I use the rest api for attachment uploading, it returns this:
The requested URL returned error: 504
I can't upload the html of it. So here is what it says:
Something went wrong.
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image is this:

The api I'm using is:
https://<confluence cloud hostname>/wiki/rest/api/content/<page id>/child/attachment/att<attachment id>/data
Sometimes it happens where the upload stops uploading the file and it is incomplete. Other times it appears to finish the upload where it gets to 100%, but then stops and appears to timeout returning the same http status of 504.