What steps will reproduce the problem?

1. move over to show bar 4 (on a hunter and a warrior) - also appears on login
2. error below appears
3. profit

What version of ShestakUI are you using? (Stating 'latest' is not useful) -

1.1.0 - latest for wow classic

Do you have an error log of what happened?

Message: ...terface\AddOns\ShestakUI\Modules\ActionBars\Core.lua:58: attempt to index global 'StanceHolder' (a nil value)
Time: Tue Feb 16 21:26:51 2021
Count: 6
Stack: ...terface\AddOns\ShestakUI\Modules\ActionBars\Core.lua:58: attempt to index global 'StanceHolder' (a nil value)
[C]: ?
...terface\AddOns\ShestakUI\Modules\ActionBars\Core.lua:58: in function `RightBarMouseOver'
...terface\AddOns\ShestakUI\Modules\ActionBars\Core.lua:139: in function <...terface\AddOns\ShestakUI\Modules\ActionBars\Core.lua:139>

Locals:

Any additional information? (example: WoW language if not English) (Attach screenshots here if available, do not link externally)

Hello, @monkeylumps. The copy of ShestakUI on Curse labeled as 1.1.0 is not from me but by a user from the Chinese WoW community. You may want to try the latest release at https://github.com/EsreverWoW/ShestakUI_Classic/releases (currently 1.0.1) and see if this issue persists for you or not.