While working on liquidsoap, we realized that using the Replay Gain slider on the Airtime web interface and clicking the "Save" button didn't have any effect. A manual /etc/init.d/airtime-liquidsoap restart is needed for the Replay Gain value to be taken into account.
As we're using vagrant-based development machines for our Airtime tests, I checked in our production systems and we have the same issue. So, to be sure, I bootstrapped a new system from scratch - still the same.
I couldn't find a similar issue on the public JIRA, so here's some quick directions to reproduce, if it's of any help!
Steps to reproduce from scratch - the way I did it:
launch a new Ubuntu 12.04.3 (EC2, virtualbox, whatever)