Wow vendor issue

I'm not sure if this has anything to do with m-boxing but I have vendor issues. The vendor don't open their windows 1/3 of the time, the don't advanced to the next page 1/4 of the time. Old vendors in old cities work fine. Nomi cooking vendor is good example, half the time he won't talk to me. the only saving grace is the other vendor right next to him. I have to ping-pong between them until he opens his window. then when I select something he may or may not actually advance.

Is this an add-on causing this or does everyone have this issue?
I now see "Nomi is bugged, try again" in the text, that seems new.
I use DBM, Jamba and healbot.

Is this something very recent, since tuesday/wednesday? A couple recent hotfixes caused some flakey stuff with some addons.

I've never had your error message, could be server side since you are getting an error message. Might be from lag if all 5 of your team is in dalaran at once.

That has happened with Nomi since Legion launched and it happens when not multiboxing as well.

You can spam click the object/Nomi/table or just click it once and wait.

If the problem you're having is just with NPCs not bringing up their dialog window at times, then this, as Ritley points out, has been a bug that's plagued Legion since it launched.