The other space eater is CDR records. CDR’s are the FreePBX - Reports - Call Event Logging; this is separate from the Call Recordings. FreePBX does not have a native way to trim or truncate CDR records so they just keep growing. These records are stored in a separate MySQL database named ‘asteriskcdrdb’. You can find this DB file(s) at /var/lib/mysql/asteriskcdrdb. Take a look at the physical files for a quick check on current size. If you are backing up the CDR with your Backup, then these are being written into that backup too.
If you are looking to truncate your CDR records a good post is: https://community.freepbx.org/t/cleaning-up-asteriskcdrdb-mysql-database/89412
There are a few gotchas to watch out for. MySQL by default was storing all of a databases tables in a single DB file. This MySQL setup would not allow for the DB file to be shrunk after deleting CEL and CDR table records. There is a procedure to change your FreePBX MySQL setup so that your MySQL DB files are stored individually. You can search the forum for suggestions on this.