WowAce

What steps will reproduce the problem?
1. Entering or exiting a vehicle while in combat.  I can't always reproduce the issue; I'll try to take a video of it the next time it occurs.

What is the expected output? What do you see instead?
If the taint occurs upon entering a vehicle, the player action bars, menu bar and other UI elements slide off the screen.  The vehicle UI slides in from the bottom of the screen, but then aborts and tries to slide in from the bottom of the screen again.  This repeats until the player dies and drops combat.
If the taint occurs upon exiting a vehicle, the vehicle UI slides off the bottom of the screen.  The player action bars, menu bar, and other UI elements try to slide into the screen from the bottom and right, but then abort and try to slide in again repeatedly.  If you manage to kill all enemies (by casting out of your spellbook or just meleeing them to death) and drop out of combat, the UI successfully returns.  Note that in both cases, hotkey assignments to the action bars do not work (i.e., pressing the '1' key on the keyboard will not activate the player hotkey 1 nor the vehicle UI hotkey 1).

What version of the product are you using?
4.0.9-5

Do you have an error log of what happened?
I turned on the taint log by /console taintLog 1 and managed to catch the vehicle UI taint in action.  I unfortunately forgot to turn on video recording.  The taint log is attached.

Please provide any additional information below.

A video of the vehicle taint in action can be found here: https://youtu.be/KIRmLNrz_cI

This would happen in raids back in the day like Amber Shaper Unsok. Back then, I didn't know about the taint log, so I had no idea which addon was causing it. I simply did a /console reloadui mid-raid to get the UI back.

Also, thanks for the great addon. My OCD compels me to align all of my frames by the pixel and I've been using this addon for years.

Confirmed

I've encountered this problem in Grimrail Depot twice recently. When I jump into the cannon during the Nitrogg boss fight, my actionbar starts rapidly switching between the regular actionbar and the cannon actionbar, again and again... only way out was that I have a keybind to exit vehicles.

I was cleaning out my video folder and found this old clip that I forgot to upload for this ticket. Just a little over a year late.

https://youtu.be/KIRmLNrz_cI