In two of our earliest Packs, the button cover (the silicone on the main button) became detached. This was due to improper adhesion procedures. While the process is now more closely monitored and an adhesion test has been added to our assembly process to Q/A that part, it would be better to have fewer adhesive processes overall as they are hard to keep consistent.
In addition, that particular silicone isn't wearing as well as we'd like. We'll be working to omit this part all together going forward with the possibility of incorporating a soft touch onto the button directly. Not only will the durability of the finish be improved, but the deletion of the adhesion process will speed up assembly considerably.
UPDATE: We've found a way to physically clamp the button inside instead of glue (big win!) and have added a more resilient texture to the surface which has tested significantly better for wear and tear.