It's a warranty issue, I wouldn't wait for an expo to inform the maker.
@ratcues is dead on and has the experience way beyond what his posts on the matter even indicate.
The cue is under warranty through the maker so I suppose it is up to their judgment if it demands a tweaking. If a $100 Viking doesn't have the issue, I don't see why a new $500 custom should.
Now my opinion, and I am no cue maker. We don't know the cue. We have no idea what the construction is. Yes, it is most likely an A joint issue, but we don't even know if the cue has an A joint. The only construction point we know is that it has a wrap.
You eliminated the weight bolt and shaft, so it's anything else. Regardless of the price of the cue or who made it, you said it is under warranty, so nobody here can really help with anything in any practical way except to say to immediately inform the maker and follow their instructions to get repair or replacement under warranty.
A buzz can be a minor annoyance with no practical impact on the function of the cue, or it could break in half tomorrow. There is no way to know for sure here.
