We have a Support Tool that will gather relevant information for us to analyze your configuration and logs. 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 ID that is shown at the end.
In any case, the issue seems very related to the application itself and not to the Bitnami configuration so I would recommend you to post the same question in a Moodle specialized forum. I believe that other people with more experience with Moodle application will know that error.