I have a little experience with this believe it or not. I dont know if this is the best thing to do, but I did the same thing and I used a lighter to fix mine. Once its cooled down, take a lighter and hold the part of the mouthpiece you want to work on momentarily to the flame. you should then be able to mold it back together with your fingers. Heat it carefully and sparingly. Once you have it back into a useable shape, allow it to cool completely. Now reheat it following the original directions, and carefully remold it following the directions. I find its real important to push on my cheeks during the molding, and to bite down firm, but not like you are biting into food. Again, this worked for me, you may not have the same results. There may be better ways to fix the issue.