[coder]

So to recap, to try to give you a logical framework for diagnosis:

- A loose /detached brace would produce a squeeky sound when pressing on the top, and the buzz wood be non-metallic, and more or less random. It woudl be dependent on frequency if anything not on where you are fretting. On a well built guitar this is fairly rare.

- Relief is the longitudinal curvature of the fingerboard. This is typically just because of the interplay of the string pull, and the truss rod counteracting it.
Relief problems are typically caused by the truss rod not being set correctly for the strings you are using and/or your playing style. Not enough relief or negative relief usually causes a metalic string rattle "fretting out" , usually in the middle region (lenghtwise) of the fretboard. Usually would effect multiple strings around the same region. Too much relief can be experienced as high action in the middle of the fingerboard. It is uncommon for moisture changes to impact relief, although (rarely, esp if the neck wood used was not properly dry, or not properly quartersawn) as the wood dries, it may then warp. Moisture induced neck problems have a more untidy effect, like the neck twisting, or the fingerboard curlig up, that kind of thing. If some moisture related neck deformation occurs, that tends to be a severe problem, and make the guitar likely a complete write-off.
The remedy maybe removing the warping neck and fitting a new one, or removing the frets and leveling the fretboard. There is no way to be sure that the wood is done moving, so it is a risky and expensive to fix.
It is unlikely that the problem in this case is the neck drying out and the the buzz is originating from this. Keep in mind you have a high-end, well built instrument, so neck warping or twisting is unlikely. I think we can trust, that the neck in this case was made out of some non-reactive species,
perfectly quartersawn, straight grained wood, that was properly aged before use.

- Nut problems. (Some) slots cut too deep. This typically causes a permanent first fret buzz which does not happen on any of the fingered notes, as fingering a note takes the nut out of play. This would have to be present from the getgo, and you just have not noticed before. This would not typically have anything to do with seasonal moisture induced wood movement. The only thing that changes the string action next to the nut is filing or replacing or altering the nut in some other way ( like the supereglue fill method)

- Action problems. Action is just the bridge/saddle being too high or low for some reason. This is often caused by seasonal top movement. Drying out lowers the action, and extra humidity raises the bridge, hence increases the action.
Basically what happens is when the top dries out it takes on a dished shape, thus lowers the bridge and the saddle, since it is attached to the top. On a "wet" guitar. the top expands, and usually takes on more of a domed shape, elevating the dridge and saddle.

Once the nut and the relief is correctly set up, the action can be dialed in last, by changing the saddle heigth. Sometimes action problems can be exacerbated by the saddle curvature not matching the fingerboard curvature, or the bass side and treble side not being dialed in correctly. ( The bass side needs a bit higher action).

- Fret leveling issues. You may have all of the above correct, but happen to have one (or a few) high frets. This can be hidden by high action and / or excessive relief, and manifest once the guitar is set up correctly. Those have to be corrected by grinding them down, using a fret rocker for diagnosis. If such service is available where you live, you can have a well setup guitar Plek-ed. Plek is a computer controlled machine, that uses computer imaging to map your fingerboard, and grinds your frets precisely, to give you a perfect playing surface. And it can do this with the strings on the guitar. Some manufacturers actually Plek their higher end guitars.
When the action and/or relief dis adjusted, it may bring out fret leveling imperfections, that were covered up by the earlier, higher action/relief. High frets may not be noticeable, until the relief and action is dialed in for optimum playability.
When you run into that problem, you can decide if you want to just increase your relief, raise the action a bit, or tackle the high frets one by one. Frets sometimes are poory installed, or poorly leveled to begin with and /or may back out of their slots to some degree, and become high over time
So the first line of defense is to tap them back into place, or to grind them down and recrown them. Fret leveling is best done by someone experienced, who has the tools needed.

Should be clear from the above that there is a correct order of diagnosing and fixing things, and attacking the "problem" in the wrong order may lead to mis-diagnosis and/or making things worse. E.g.: you should not start fret leveling until the relief and the action is set up. You should adjust the relief before worrying about the action. etc. etc.

The most common dynamic / seasonal changes are the action changes, usually associated with:
- neck relief changes, commonly resulting from switching to a different gauge strings
- air humidity induced top movement, resulting in action changes.

Another thing: If the guitar is subjected to heat, such as, left in a car in the summer, some permanent changes may occur. This is because the glues typically used in guitar construction are thermoplastic (they soften when heated) . Guitars with no truss rod are especially prone to this type of re-arranging themselves. A hot guitar may distort its shape, as the softened glue joints are subjected to string tension. For example, the neck may take on a permanent bow, and set in that position as the guitar cools off. The opposite may also happen, e.g. the guitar is stored or shipped with the strings losened, and the truss rod under tension. As the glue softens, the truss rod may force the neck into a back-bow position, because the balancing force of the strings has been removed. The guitar neck then may "set" in a back-bowed shape. This is why I do not believe in shipping guitars with the strings losened.
Something like this can even happen if the guitar is just left in a sunny spot and heat up from that. These permanent shape distortions are hard or impossible to fix for a non-luhier, or even for a luthier, because it is difficult to control what happens when the glue is softened. An inspired luthier may clamp a neck to a caul and carefully heat it up to reverse heat damage. I would not dare to do this myself. Just too many way things could go sideways, esp. finish damage, or parts falling apart...Ugh.

Factory made/mass produced guitars tend to be set up conservatively. High action is usually not a "warranty return" offense, but severe fretting out is. So that is the obvious side to err on. OTOH luthier made or custom shop instruments tend to be set up fairly aggressively.
I oft hear the term "just north of buzzy". So when conditions change, the factory made guitar may still have high action, but the "custom" instrument may end up fretting out.