Responsive Firewall blocks just one of my external clients, after a few hours

I have the responsive firewall enabled.
I have 12 external clients, but one of them - just one, keeps getting flagged as ‘attacker’, and then ‘clamped’. and blocked.
I clear the block, it then shows as a known-registration, but then a few hours later it’s blocked again.
I grep the asterisk full log (which includes Security log information from what I can see), and I don’t see anything negative relating to this IP address so I don’t know why the firewall is deciding that this one host is naughty.

I have saved copies of all the asterisk, freepbx, dmesg, /tmp/firewall stuff etc. Any ideas where to look or what to post?

I have added the IP as a trusted zone for now, and it is static anyway, but if my logs would be helpful then i’ll post them.