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