After the recent patch, I decided to revisit Taffington and build out over as much of the water as I could.
Previously, I'd tried to move all of my trade booths and vendors out there. I vaguely recall some wouldn't even take up their positions. Did I not give a clear enough path? I don't remember now. But the ones who did stand at their posts wouldn't actually interact as vendors.
So this time I tried again, and made it big, with lights and outdoor seating near the Tier-3 Restaurant. Once again, the vendors did move out there to take their positions. However, the only vendors that interacted as intended were the ones working the Tier-3 Clinics. Every other vendor was all "huh?", "I hope you aren't here for me", etc. So I built up the open land in front of Tarrington and restationed them there. Then I built up the waterfront deck to be a new dwelling place, and moved the necessary beds out there. The settlers *mostly* seem to use the beds (a few stood in the beds despite being asleep - but that's another bug AFAIK).
This "hydrophobia" doesn't seem to affect vendors stationed on preexisting game assets: I have a Tier-3 Restaurant at Egret Tours Marina built out on that boardwalk, for example, and the vendor interacts as intended.
Has anyone else had this type of behavior? I've only tested at Taffington (that's where feeling cramped for space motivated this design choice).