• Open VisualEditor with New Vector enabled
• Create a link at the start of a line
• Put cursor inside the very start of the link

What happens?:

Arrow pointing at the cursor is off the edge of the popup.

What should have happened instead?:

Arrow pointing at cursor is within the popup

The arrow is in the right place, but the popup isn't being positioned appropriately to match it. I'd speculate that the overlay or the context are getting shifted from their expected position somehow.