What a coincidence: the same model (though 1µF/450V) has failed in my room fan last week
. I’m waiting for a new one to arrive, along with a thermal cutoff that died with the capacitor. It seems that you’re luckier than me: yours have solderable pins, while my have wires potted. Actually the whole fan, from the wall plug to the windings, is made as a monolithic unit. Not even a single point where you could probe it without cutting wires.
That is not something unusual and is not an indicator of a bad design, unless you can prove that in some model they fail considerably more often than the typical rate. Run capacitors are under stress even higher than start capacitors and they break from time to time. Just replace with another one of the same capacitance and voltage rating. Preferably with the same model — run caps need possibly low serial resistance and take not very favourable working conditions, so using just any 0.8µF/400V cap may not be the best idea.