Client Character Position Desynch

Originally posted by [b]theultramage[/b]
http://www.eathena.ws/board/index.php?autocom=bugtracker&showbug=2013

For way over a year now I've been encountering the following situation:
1. you're in town
2. you decide to rotate your char towards a certain direction
3. you do shift+leftclick on some empty cell
4. your char starts walking towards a merchant 1 screen away.

Today I noticed what exactly was happening...

Here you can see that when I hover over the empty cell below the kafra, the client shows the nick/party/guild of the merchant on the bottom right. Holding shift will change the cursor into 'attack', and shift+leftclicking will initiate follow/attack movement towards this char.
What the screenshot doesn't show is that when I stood in one other particular location and had my camera zoomed just right, the client chose one merchant in the bottom left part instead. So it's rather messy...

I wonder what could be the cause of this glitch...