It's a normal thing to happen to a piano for countless reasons from the humidity causing a buzz to the fallboard or front cover shifting a miniscule amount, regardless of the piano being new or old. But that doesn't mean you have to live with it.
The trick I tell people to try to find a buzz is have someone else play the piano while you walk around and listen. It might not even be the piano! On my own Walter, I will get a buzz sometimes, but if I press hard on the right side of the front panel and let go, it will go away for another year or so. Another time I heard a buzz, and it was actually a light fixture 15 feet away on the ceiling even though I swear it was coming from the piano. I had my 9yo play the piano so I could walk around the room and find it.
Good luck and update us when you find out!
P.S. If it's something inside the piano, don't chase it down and fix it yourself. Wait for your tech to come back. Something in the wood may need to be shimmed, for example. (My old Kawai console needed shims under the fallboard/keyrail thing from time to time to stop buzzing.)
I do music stuffsYep, I have a YouTube channel!
1998 PETROF Model IV Chippendale
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2017 Charles Walter 1500 in semi-polish ebony
1991 Kawai 602-M Console in Oak