OK, if the button doesn't feel right then it may well be the switch, especially if it was working then suddenly stopped.
The problem is, the warranty.
If you try to replace this part yourself, you will not only have to do the work, you will also have to buy the part. This will then invalidate the warranty, should you have a larger problem.
I understand that its not ideal, but I really would recommend that you get them to repair this for you under the warranty.
Sorry there wasn't an easier solution for you on this one.
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