Some time ago i noticed that the knob for controlling the wet/dry effect of the BPM effects is loose. As seen in the video its not completely secured in place, i don’t remember this being a problem when i got the mixer.
It also makes kind of a “crunching” sound when i tilt it around which makes me think it’s not good. Has anyone else had this problem?
So what do i do with this? Return the product? Fix it myself somehow? Wait for the knob to break completely and hope i still have the warranty?
How do you move your gear? Pro flight cases?
You thought you had a glitchy headphone socket last fall , and now this loosened wet/dry knob. Both things near the front edge of the x1800 mixer. Could some foam or packing/storage solution be pushing too hard against that front edge? A mis-moulded decksaver? Headphones stored inside flightcase in that zone? Heavy touch friends ?
The glitchy headphone socket was not a glitchy headphone socket, it was a faulty cable and that issue was resolved. I don’t move my gear at all, i don’t use a flight case and i don’t have any friends.
So no, this problem can’t be traced back to mishandling the mixer.
If this one loose knob is the only problem wit the mixer then since it’s purchasing then that’s not too bad. It does need sorting but if your mixer was imported the wRranty is only with the country it came from judging by the advice given on other posts
One of my filter knobs has developed the exact same issue minus the weird crunching, really annoying especially considering that my gear has never been outside my man cave, and i only got them in December.
So what to do about this? 
If it’s imported then you’ve got no warranty - best talk to your dealer where you got it from
I can’t tell you what to do.
What i will say is that there is more going on in life right now which is more important, and i stress that this is my opinion only, if your Mixer is in warranty then i would request support from Denon regarding that fact.
Best of luck with it friend and be safe.