To finally gain the Sanguine Feather Quill of Lana’thel one must complete the “Brush With Death” quest. You accept the quest then you’re meant to click on the quill, become a pen (with action bars replaced with vehicle bar) and trace out runes.
What is happening now is you are ported to the first rune, but no vehicle bar appears and you remain as your toon avatar and don’t become a pen. It this point you’re stuck. You can’t move or achieve anything. The only escape is to abandon the quest. Has been this way since the Shadowlands pre-patch.