switched to peaceful with wither active and had problems

• I summoned the wither
• died
  -exited to title screen
  -exited the game
  -loaded the game
  -respawned
  -changed mode from normal to peaceful
  -noticed all the trees, grass, cacti, my doors, ladders, wooden pressure pads were all gone
  -i started to dig through sand
  -the game froze
  -i force exited the game
  -i reloaded the game
  -same problems again