If this is still not working for you, can you see check to see if the user running the app has permissions to add attachments via the SharePoint UI? If this is not the issue, can you share your session ID from a PowerApps session where the add attachment failed?
@NigelP So does the problem appear only on the Galaxy S8? Are you able to add attachments when you run the app in a web browser? Are you able to add attachments to the SharePoint list directly though the SP UI?
To get the session details, see:
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