For the last couple weeks when I get a notification vibration, the long heavy vibrate, it sounds like the back of the phone is loose. I have checked everything I can, removed battery cover and such but to no avail It sounds terrible.
I haven't had this experience. If the back feels tight, then could it be something vibrating inside the phone? I'd get a replacement because, if something is loose inside, I would think it could get worse over time.