Just FYI, the firing button lights up from the side. Maybe you just haven't noticed before.
There is a little LED on the circuit board to the left of the base of the button that lights it up, the frosted finish of the button makes it diffuse the light as if the entire button is lit.
Also if my finger isn't on the button and I shake my Provarii, the actual button rattles..... this is normal. The button isn't spring loded, but instead sits freely on top of the micro momentary switch of the circuit board.
The tight tolerance of the button hole in the tube and the buttons larger diameter at it's own base are the only aspects that keep it in position. Less wearable parts = less opportunities of failure and better dependability.
I suspect your Provari is fine.