Help with sounds

[Kos92]

I have an i910. The problem I have been experiencing for the past 3 months occurs when I receive a text message, mms, or email. I have alarm 4 set as my sound for a text. The omnia is set to play the tone and vibrate but often it only vibrates and there isn't any sound. If I use a longer ringtone, it will only play a part of it. For example, if I have a tone that is 10 secs long, it will play like 2 secs of it and stop. After that the phone makes a buzzing noise out of the speakers and the phone vibrates slightly. The odd part is that when I receive a call the ringtone plays perfectly. Can anyone help with this or give me a clue as to why it happens? I have given the phone a hardreset but it still does this. Idk if this is caused by a setting or corrupted files or what. Please help

thx