I have been in tray 1 for 3 weeks. I was in that tray for that long because I was away from home and didn't have my tray 2. When I went to switch to tray 2 my trays went on easily. However, my last teeth in the back of the top does not fit. I do have a crown on that tooth. The tray is super big and it hangs down. If I bite down it makes a suction sound. When I open my mouth the tray pops off that tooth. I'm assuming this isn't mornal. Is this okay? Any advice on how to fix this?