Won't let me respawn.

I built a huge castle that took 2 hours and now it is lost. I did /locate buriedtreasure and then teleported to the coordinates given. I accidentally went to 712 200 792, which was too high up. I fell and died. So I clicked respawn. But it respawned for a millisecond before going back to where I died and asking to respawn or quit again. I clicked respawn over and over and it didn't work! Please fix it, I love my castle!

PS it was Update Aquatic Phase 1, in case I got the version wrong.