That seems a bit irish if you'll pardon the expression, vibration and thumps stop it working so you need to thump it to get it to work?
My experience of powder extinguishers is quite different, mine used to be on the old boat mounted on the seat back, at least until after a couple of years someone whacked it with some diving kit and set it off. What a mess it made even after grabbing it and launching it still going into the briny.......
My wish list includes a Sandra Bullock cheap, anybody got one of those lying around in the garage................