What steps will reproduce the problem?

1. Install latest version from master zip
2. Observer Quest Log (L)
3. Quest Log appears with Blizzard UI frame, not ShestakUI
4. Also Quest Tracker +/- button does not hide tracked quests

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

1.13.2

Do you have an error log of what happened?

No

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

Spellbook, Social, World Map, Pet, Reputation, Skills also back to normal.

I believe this is a conflict with some other addon you're running. Try running ShestakUI with no other addons enabled and make sure that styling of Blizzard frames is turned on.

This is what i got with just ShestakUI