I think the problem was never fixed, or if it all someone claimed it was fixed, it was never tested properly.
I am certain that this problem is back again on my phone. I found out that my phone's number lock keypad freezes and fails to display the touch sensing display areas for the numbers pressed.
This happens more so often immediately after a call is disconnected and you want to access the phone - noticed 5 times so far !
I really think it is indeed an IOS issue.
It is shame that simple important phone features are going for a toss when Apple attaches bells and whistles into a phone - This is ridiculous of apple, you are definitely draining your brains to innovate at the same time never realises a customer are missing basic features required to make/answer and use a "phone".