What about the PHP / webserver logs. The two places you were looking for errors are not directly related to where you might be having problems. I'm not 100% sure where the 2.5.1 logs are stored since I really started delving into the code post 2.5.2 but I believe it is stored in the zendphp.log there. That might have a more useful error as that is where any errors the web interface might provide are located.
Nothing in the apache log. About the zendphp.log : When I add a new show, my browser crash but I see nothing in the log. The new show is created when I reconnect. When I delete a show, just before stuck my bother, a line appear in the log : 2016-01-27T15:28:26+01:00 INFO (6): [ScheduleController.php : eventFeedPreloadAction() : line 139] - month
If I search for errors in this log, I find some occurrences like this : [index.php : () : line 73] - #0 /usr/share/airtime/application/forms/AddShowWhen.php(274): exception_error_handler(8, 'Undefined varia...', '/usr/share/airt...', 274, Array)
Anyone reading this a find it funny about my grammar , I make no apology ,Go get a translator. "The Problem with education today is that it takes a university degree to switch on a light bulb" "You learn from your mistakes but wise people learn from others mistakes avoid Making mistakes there is not sufficient rooms to make them" "Innuendo","If's","Assumptions" and "Fear" are for politician.Who,What,where,When and How are for those seeking knowledge and care about Humanity. "I might be in Mud but that does not Make me a Wild Hog(pig)" “Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius — and a lot of courage to move in the opposite direction.” "The only thing that remains constant is change itself" May the force be with you,until our path or destiny bring us in tandem.
On the interface code ? no. The only change I made is applying this script about recording sound without soundcard. I can disable it but I don't think is linked to my problem ?
and noticed there were some differences, specifcally relating to this issue. So I just copied the github file to my server and it solved the issue. You might want to check/diff these files too as it may solve your problem.