I ran into this a couple of years ago. I decided to just create my own keyboard in construct and use that instead of relying on iPhone's keyboard. Apple doesn't care how well anything works if it's not their own app, they constantly break things with updates. like they have chimps testing these things.
So whenever possible do everything yourself. It is not that hard to design your own keyboard and once you do you can use it in every game. Less that 2 hours of work for everything, including graphics.
You may find a solution for it today, but pretty guaranteed that they will break it tomorrow