Was testing a Hardcore Server for me and a few friends.

Upon Death, I was able to respawn momentairly but then after a few seconds was placed in Spectator Mode.

Upon entering spectator mode I was rendered unable to move, no chat elements appeared unless I explicitly opened the chat, all terrain was turned invisible, and All animal entities began spinning wildly nonstop and stopped moving. Sound was unaffected.

This issue persists after relogging.

If the player is set to Spectator mode without dying: The terrain will unload, however, you can move around and collide with the terrain, mobs will move around normally, and chat elements will not break. However, upon relogging into the server they will break entirely.

If the player is set to any other gamemode during this bug they will need to restart the game to see the terrain again. 

Other players report extreme lag spikes when near a player in spectator mode it seems as well. 

The screenshots do not properly show the animals spinning, but it is occuring.

Edit: The player will also be suspended in the air when they switch gamemodes from spectator to survival during the glitch. Once the game is restarted and they relog they will fall as they should have. (This may cause the player to be kicked for "PLAYER was kicked for floating too long")