In order to find a final fix to this issue you will need to do the following:
1 - Install the Organization Insights - It will give you a clear view of which entities are consuming the most data.
2 - Once you know which entities are using data, you should assess whether or not to clear the data from the entities using Bulk Delete. 2.1 - If, the entity in question, fills up periodically, setup recurring bulk delete of old records.
3 - If the Audit base entity is the one taking up space, please review audit configurations.
4 - If email and attachments are consuming data, please verify the current Email Synchronization setup.
5 - Every other custom entity, completed system jobs, and plugin trace log can be removed.