Occasionally, an experience orb will simply follow the player around and not be immediately collected. 

When this happens, the orb will fly towards the player but will then hover at their feet instead of being absorbed. When the player moves, the orb will follow. If the player moves faster than the orb, eventually the orb will be left behind, remaining in its position. Upon approaching a left-behind orb, the odd behavior will resume.

Orbs that show this behavior eventually do become collected after a long period of time (usually a minute or two). When they "decide" to be collected, it doesn't matter how far away from the player they are. For example, the player can run from the orb, leaving it some distance away, then it will eventually sink into the ground at that location, the collection sound will play, and the experience bar will grow.

I'm not sure what triggers this behavior. It's relatively rare. On the order of 1 in 100, as a guess. It seems to be associated with specific orbs; that is if a given orb exhibits this behavior then it will continue to do so, it won't suddenly function normally.

This behavior is not new with this version.

This happens in single-player games and does not seem to be correlated with lag in multiplayer games.