I am using the Sourcefabric version with the appropriate sources.list entry. Airtime! version is 2.5.1 i am having the same issue (along with a few others that i cant seem to resolve)
i have ran the apt-get purge airtime icecast2 several times (took me 3 times to get into the web panel as Apache2 wasnt setup correctly to begin with) this last time i decided to purge icecast2 + airtime to see if that would fix it, however after re-configuring it looks like it ran for a few minutes and then liquid-soap crashed, its been stuck in a loop ever since. No settings have been changed in the console everything is factory default out-of-the-box. I have checked every setting i can imagine in every configuration file i could find (aside from knowing what to look for) everything seems to be configured correctly. At one point it looked like it was having a

Connection failed: could not write data to host: Connection refused in write()

error however a quick look through the Web UI let me change that in the stream settings that seemed to fix the issue and i had green lights across airtime-check-system I added a show and set up a playlist after setting up a watch directory and at the time of the show nothing happened. so i checked log files ran a loop to watch the output of the check-system sudo watch --color -n 0 airtime-check-system the issue seems to be tied to

LIQUIDSOAP_PROCESS_ID          = FAILED

thats when i noticed the little printout of the log file in the check system command running sudo tail -f /var/log/airtime/pypo-liquidsoap/ls_script.log gave me a giant amount of useful information (full log files can be found on my github seems Sourcefabric cannot post issues on there's) Also it seems to me that the file playout history is NOT logging files. If this function actually works it seems the issue is that the player is not playing. Which is odd due to the fact that the Now Playing tab clearly shows a counter and the currently playing track (or is it not playing the media and just THINKS that it is?) i have no idea how to check that last question as Icecast reports source_client_connections 528 and counting the currant connection is still 0 however every now and again a source pops up in the index (as shown by the icecast_Source.txt on the github link above) i do know that Icecast is functional and works with its currant configuration as both Sambroadcaster and MPD can connect and set up streams I am also able to move listeners back and forth between those 2 streams. I have also built my own DNS using bind9 due to the fact at one point i could not even access the Web Interface. If you require anymore information on diagnosing this issue please let me know.