Same here - I am on a fresh install of Raspbx and after updating all modules and configuring FreePBX my logs are now also filled with those. I get multiple per second so every day results in 100MB logs for a PBX which is not even in use yet…
Edit: solved - the problem is that my PBX is being scanned / brute forced by external servers (in this case from China) where it seems they try to guess extension codes. This was visible by the many entries in the security logs. I fixed the issue by blocking all SIP and other VoIP traffic from sources other than my SIP trunk provider (using iptables).