If the problem persists after modifying the permissions of the folder again, it's not a permissions issue. Regarding the upload issue, instead of sending only that file, we have a Support Tool that will gather relevant information for us to debug the issue. Could you please download and execute it in the machine where the stack is running?
These are the links to download the tool.
If you are using a console, just type the following to download the tool:
wget -O bnsupport_tool https://downloads.bitnami.com/files/bnsupport/0.1.0/bnsupport-linux-x64.run && chmod +x bnsupport_tool && ./bnsupport_tool
The output of the execution of this tool will be a zip file with all the information inside. Could you please send it to firstname.lastname@example.org ?
If you are working with a remote instance and you do not know how can you download the zip file from your instance, you can follow this guide to download it.