One baseboard banging.

Good morning all,

I have a customer who has one individual piece of cast-iron baseboard banging. The boiler was just replaced about 2 weeks ago. We flushed the boiler before installing, skimmed after installing and came back about 4 days after to skim it again. We didn’t add any SteamClean or anything. The banging happens all the time, and not just while warming up. And the I’m wondering if my guys didn’t give the one piece of supply piping enough pitch. I will attach a few pictures. First picture is the previous boiler. The second is the new boiler, and the 1” copper line is what goes to the baseboard.