For many owners, one or both of the buttons either feels odd, doesn't work, or falls off.
They are pushing on little micro switches, not metal bubble switches, inside the case surface mounted on the main board. Sometimes the main board is slightly misaligned and the pusher from outside misses the switch on the main board. Sometimes the surface mounted switch is loose on the main board.
You will need to get the watch replaced if the surface mounting has failed. It might be possible to re-align the main board.
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