Environment: wagon does not destruct properly

In one of the "Old Tristram Road" areas shortly after you leave town, there is a breakable wagon, always in the same place, that doesn't destruct properly. When you enter the area for the very first time during a single session, you strike the wagon and pieces go flying, but the wagon itself remains untouched on the screen; if you go back later during the session, it breaks as it should.

Screencap of its location: http://i.imgur.com/kXyjz.jpg