Thank you for using Bitnami. I just launched a fresh Bitnami instance with the latest version of Moodle and I could create an example course and export it properly.
After that, I also downloaded the backup file without problems
Could you please create an example course and check if there is an issue when importing large courses?
We have a Support Tool that will gather relevant information for us to debug the issue. Could you please download and execute it on the machine where the stack is running by following the steps described in the guide below?
How to Run the Bitnami Support Tool
Please note that you need to paste the code outputted by the tool in your reply.