The encounter introduces a new button within the Alternate Power Bar. The bug seems to be related to this (ExtraActionButton1).

3x tullaRange-4.2.0\tullaRange.lua:277: attempt to index local 'nt' (a nil value)
tullaRange-4.2.0\tullaRange.lua:251: in function UpdateButtonUsable' tullaRange-4.2.0\tullaRange.lua:227: in function <Interface\AddOns\tullaRange\tullaRange.lua:225> <in C code>: in functionActionButton_UpdateUsable'
Interface\FrameXML\ActionButton.lua:517: in function `ActionButton_OnEvent':
Interface\FrameXML\ActionButton.lua:141: in function <Interface\FrameXML\ActionButton.lua:139>:

nil

Locals:
table: 30B356A8

1x tullaRange-4.2.0\tullaRange.lua:277: attempt to index local 'nt' (a nil value)
tullaRange-4.2.0\tullaRange.lua:251: in function UpdateButtonUsable' tullaRange-4.2.0\tullaRange.lua:227: in function <Interface\AddOns\tullaRange\tullaRange.lua:225> <in C code>: in functionActionButton_UpdateUsable'
Interface\FrameXML\ActionButton.lua:249: in function <Interface\FrameXML\ActionButton.lua:231>:
: ?
: in function ActionButton_Update' Interface\FrameXML\ActionButton.lua:478: in functionActionButton_OnEvent':
Interface\FrameXML\ActionButton.lua:105: in function <Interface\FrameXML\ActionButton.lua:98>:

nil

Locals:
table: 46243468

The latest version should resolve this issue.

It does....also fixes the impossible lag caused by the older version. Signed up just to confirm in case you get any other comments about it. Very nice work getting it updated so perfectly!

For reference, the lag you were experiencing was actually caused by the error message happening repeatedly :)