I had one Silicon shell that worked great with 2-K3s But with the 3rd one it keep causes the K3 to re-boot! The K3 is 2 yrs old works Great Except in the Silicon case ...weird! I had another I use on both Fire HD 7" & another that made its rounds on 3 different Sony readers. No problems.
I thought about Super Gluing the case on the Fire

But did you know you Have to take the darn thing out of the case to get into the SDCard? Well you do

so super glue wont work