Hello,
Is not an easy task to synchronize backend and frontend via AJAX, probably is necessary a carefully debug in your code, from since the user clicking, until the database insertion. Most likely your problem is frontend because of your code is not supported by the new browsers or something like that. Anyway, I'd like to know more about your issue and propose a schedule for the solution. I'm available to start to work right now.
Best Regards,
Fernando.