Sometimes, after long bus or car rides, I find that the 1st valve slide on my trumpet has fallen off in the case. Fortunately, no damage have been dealt yet. What is causing this to happen? Does anyone else have/ have had this problem? How can I fix this? My horn is a ytr-8335las (Yamaha Wayne Bergeron model), the case is a Yamaha double case, and the lubricant used on the 1st valve slide is a combination of Ultra Pure light slide grease and few drops of Ultra Pure valve oil. Also, I'm planning on getting a Torpedo Bag tomorrow so I worry that it would fall off easier.