MAINLINE

To reproduce:
You just need to click left or right the friends button(wow or bnet friends) at will, if you find If you find the TARGET function disappeared, it means tainted.

When tainted occurs, right-click friends button have no TARGET.
It will prevent you Set focus, RAID_MAINTANK and RAID_MAINASSIST in FriendsFrame‘s Raid, and pop the statickPopup frame—— Because the dropdown is tainted, Of course not call FocusUnit().

I haven't figured out the specific cause of the taint, But I think it should be related to FriendsListFrameScrollFrame.
But I know how to solve it, just delete Friendslistframescrollframe section. Maybe you have a better solution.