3971rd galley tank odor drain loose?

[Ol' Alvie]

I have a 2018 3971rd with the center Island and separate galley tank. After arriving at our destination last year, my lovely wife was running water in the sink and found that it was running out on the floor from the drain. During our trip, we had traveled on a particularly poorly maintained highway and it had shaken the drain plumbing under the sink loose. I was able to re-attach everything and clean up the mess but ever since then, whenever we run a vent, it creates a negative pressure in the cabin that creates an especially nasty funk. There is no doubt it is coming from under the sink and I have removed and inspected the anti-siphon trap vent and all looks pretty good.

I have a suspicion that the connection between the sink plumbing and the galley tank is not solid. I think this because I can grab the drain pipe that goes into the floor and it moves fairly easily and I think the smell is coming up through the floor where the drain pipe goes through (although I can't confirm it). Any ideas on how to resolve or confirm other than pull the belly and check out the galley tank? Has anyone else had this problem?