If got some issues with the vehicle state of bars.
Sometimes my main action bar doesn't change to the vehicle state and I can't click any buttons of the vehicle since it stays in it's default state.
/neuron state tells me correctly that the bars states are vehicle and stance (I'm a druid)
The exit vehicle button on the other hand always shows correctly, so it appears to recognize when I'm in a vehicle.
This error occurs sometimes random on vehicles i've already been in and were working correctly before.
In these cases what usually helps is to enter configure mode by left clicking the minimap icon and immediatly exiting it. This appears to force the bar state to reload and fixes the problem.

There are however 2 occasions (so far) that the error always occurs in and is neither resolvable by entering the config mode as described above nor by reloading the whole interface:

1. During the quest "In Every Dark Corner". This is the first quest after finishing the 4 world quests for the horde incursion on Drustvar in which you get empowered by the voodoo masks and need to slay alliance troops. I can only do this quest by disabling Neuron.
2. When I am entombed during the boss encounter "Mchimba the Embalmer" in Kings' Rest (2nd boss).
   I need to disable Neuron before this boss otherwise I am unable to signal my group where I am.

is this a duplicate of #430 ?

Interesting. I don't know those two quests off the top of my head, but I believe you. It's hard to pinpoint issues like this when it's just very specific scenarios when the issue shows up. Let me try to find those quests and see if I can replicate the issue

I am having the same issue. At first I thought it was just with the Tortollan "Circle of Life" daily where you are suppose to move the crab. The bar state changes to, I assume, vehicle but I have no buttons and the buttons that I am suppose to be able to push to move the crab do not work. Now it is also doing it with the Rustbolt "Nukem Norbert" quest as well, Bar state changes but no buttons. Maybe it does it in other vehicle or possess quests as well and I have just not found it yet. Reloading the UI does not fix it. I am using the English client 1.2.1

So I have been able to access the vehicle buttons only if I enable the blizzard bar and reload. Then the button numbers do not work.It says they are numbered but pressing the 1, 2, 3, etc does nothing I have to manually mouse click them. They also, still, do not show on the Neuron bar which is designated as a vehicle or possess bar.

PS. All visibility states are checked.