Gamepad Vibration fails to play if too much is going on
If a gamepad vibration is currently playing, but there's a lot going on such a loading a new area, hitting an enemy, vibrations will suddenly stop. T
The issue seems to be present both when an Addon plays a vibration, and in vanilla vibrations (a notable example is with restoration staffs where the continuous vibration during attacking can sometimes stop).
Just in case you did not already do this:
Raise this bug report ingame via the chat command /bug as well.
The addons here are not an official bug report to ZOs, it's mroe about the addons and API related stuff.