I have a nexus 5 on t-mobile that is running lollipop. Most texts I receive have the sound notification like its set up for. However once in a while i will not receive the sound and it will only vibrate. This seems to be completely random. I don't believe its a contact issue because I may get 3 or 4 audible texts alerts from someone and then the next when will only vibrate. I am using Chomp SMS is my text app. Has anyone else had this issue or no a solution.