For my adventuremap I use a mechanism, which teleport a dead player and sets a new spawnpoint at the new position. Whenever I do this, weird things happen:

• The screen is shaking at the place, where the player died
• The screen is shaking between the dead-location and the teleport-location (very fast)
• The player sometimes gets respawned somewhere else; sometimes with the message "Your bed has been occupied ..."

I guess that you should be allowed to teleport players without any problems, so I call this a bug.