I don't know how common the failures are on these but I have gone through 2 of them in pretty short order. I'm not going to spend $20 on another one when I've not been happy with them.
The issues I have are :

1. Hard to open and close
2. "Sticky" to put things in and get out
3. Tear far too easily
4. Did I mention expensive?
5. Loss of fine grained touch screen sensitivity

This was the solution I came up with. An extra benefit of this is I can store maps in additional ziplocs and just move the internal strip to swap out map sets. Super cheap and works just as well, actually, better.

I hope this is useful to some folks or gives you ideas of your own. Enjoy.

YouTube Video of Ortlieb Map Case Replacement