In your question you have said that you restored your phone from backup.

I am guessing that when you restore the backup, it is restoring the problem as well.

I think that this type of problem should be able to be solved by restoring your phone and setting it up as a new phone and then syncing everything across to it.

Having said that, I am not sure what will happen with your purchases when that happens.

If, after that, the problem still occurs then it is time to contact apple for a warranty replacement.