filesSaveUrl failing with invalid_url error on valid, public URLs.

We have an oauth integration with Dropbox that generally has been working fine - recently we've started getting the following error on uploads from the node SDK (filesSaveUrlCheckJobStatus call):

{ '.tag': 'failed', failed: { '.tag': 'invalid_url' } }

We haven't changed anything on our end around the implementation, and we've confirmed that the URLs being sent to dropbox are correctly formatted and publicly accessible.

e.g. argument:

{

    path: '/public/60848ed9e0d1da0d770ac660-myfile.pdf',

    url: 'https://s3.amazonaws.com/pf-pdf-01/1/2021-04-24/yw13f4x/mksMz31N9JSmqWSJ9Wqt/myfile.pdf'

}