May have been posted before but I couldn't find anything.

Attached video .flv file (not playable in windows media player I believe, but other players like VLC should work) the video quality is poor, but you do see what is going on. Also, the audio isn't important.

The video was recorded in 15w49b, but the problem persists in 15w50a. It might also happen in earlier snapshots (and probably does)

Steps I do to make this happen (on my pc, anyways):

1. Start minecraft
2. Load up a world
3. Exit said world (any amount of time, can be done after 2 secs or 2 hours)
4. Open another world (again, any amount of wait)
5. Bug happens

In order to fix it I simply have to restart minecraft. Not a huge problem, but constantly having to restart minecraft is annoying to say the least