One more thing you could try is installing the addon MoveAnything.
It’s usually used to move frames around or hide them. But in your case you could try to use it to reset the objective UIs position.
Give me second. I’ll head ingame and look for the appropriate options.
Open the MoveAnything menu via Esc > MoveAnything .
In your case you’re probably looking for Achievements & Quests > Objectives Window.
If the reset button does not show up, try clicking the Mover or Hide checkbox to make it appear.