This is really hard to describe; let me know if you want a video or something.
When you click and hold on the ground and then drag the mouse through an exit or the Town Portal, the character will instantly teleport through said exit/portal, even when the character isn’t anywhere near it.
I am able to repro this every time by going through a Town Portal to the The Council Chambers in the Ruined Era, clicking on the ground, and dragging my mouse through the town portal (even with my character on the other side of the screen).
A more interesting case: go to Precipice in the Ruined Era, via the usual teleporter thingy. Click anywhere on the ground and hold. Now, without releasing, move your mouse between the teleporter pad, the Old Barracks exit hitbox below, and the Ancient Cavern exit, without actually letting your character reach any of them. After a few movements, you will find yourself entering the Old Barracks, which is clearly impossible from that position.