"it now works 9 times out of 10"
That's not acceptable, it should work every time, all other things being equal.
A two-week old machine shouldn't need to go for repair unless there's a hardware fault. The retailer has already reinstalled software, and if that didn't work either the software is faulty, or there's a hardware fault. Ask for a replacement machine on the basis of this one not being fit for purpose.
You don't say where you bought the iPad - it might be helpful to know that.