upright actions can be more sensitive to humidity at least in respect to the jack resetting.
what you can do is shim the hammer rest rail just enough such that there's a tiny bit of lost motion between the hammer butt and jack. this will give it the clearance such that it will always reset.
there are other elements of regulation you can play with, but this is very involved and highly variable from key to key, it's alot of self-teaching/ learning.
acoustic actions usually has to be regulated at least ONCE in the first year, then every 2-3 years. by the 10th year, it'll be more/less pretty stable, and you'll need regulation less often.
it also depends on how much you play it, the more it's played, the faster it goes out of regulation.
this is why i think, only highly capable/ technical owners are compatible with acoustic actions, because otherwise, you'll just have that 1 key, or a set of keys which always need a little fiddling to feel right. if you can't do that yourself, then the alternative is to be a millionaire and hire the piano tech to come over all the time. 😗
for most owners of acoustic pianos, they're actually playing a very "mechanically sloppy" instrument. it doesn't matter what brand or how much it costs. it's just the nature of the machine with so many components that swells and contracts from humidity.
piano is a unique instrument in that most pianists are helpless when it comes to the Machine itself.
only engineer guys like cybergene, can ever attain consistent stability because they're capable of tweaking any problem at any time. the action is never perfect and it can drift fantastically and unpredictably.
Digital piano's simplified actions, are the best for no maintenance stability. they drift very little unless you do deliberate damage. This is with exception to kawai's RM and Grandfeel actions, these are unstable, and require a similar degree of regulation/ maintenance to stay consistent.
