I use Dominos to change the position of the Extra Action Button. However on load ExtraQuestButton resets the position, ignoring Dominos positioning.

If you try to move the button from your addon it does recognise another addon has moved it and does not allow you to change the position.

In Anchor.lua you have the following lines

-- re-anchor/size buttons
ExtraActionButton1:ClearAllPoints()
ExtraActionButton1:SetPoint('CENTER', self)
ExtraActionButton1:SetSize(self:GetSize())

However there is no check for other addons like when you go to move the button.

I just copied the code from above and added the check to stop the reposition always firing on load and it has solved the issue.