"The IP 10.1.5.12 has just been banned by Fail2Ban after 6 attempts against SIP on freepbx-a."
On a specific number of false login attempts to FreePBX GUI, Fail2ban bans the IP and sends an email notifying the administrator. The text in the email says it banned the IP after attempts against SIP, which is not the case. It should say that it blocked the IP after attempts against FreePBX GUI or something like that.
The text should also differ between login attempts to FreePBX GUI and UCP.