Confirmed that this action happens also using the default UI. I believe then it should be happening no matter what UI is being used. I would expect that Drums, Fetish, and other popular UI's are experiencing the same issue. This is confirmed across several raiding guilds. Its def some kind of refresh issue that may or may not be related to the chat windows. I don't know if there is a work-around or even how you could duplicate it outside of a raid enviroment
Have at it! heheh