Hi,
Thanks for posting in Q&A platform.
Before we go further, may I know if Windows client has encountered the same issue?
Please check if the NTFS permission for Android user is including Read & execute, Read and Write read in the shared file's properties.
And then please check if the Android user has read/write permission.
If the user has these permission but still cannot write and upload file, I would suggest you follow DSPatrick's suggest to enable some auditing to capture more for further troubleshooting.
Best Regards,
Sunny
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