Stopped rendering, mobs frozen, save never completed

spawn was around 0,0. I don't know the seed. started out fine i ran around doing the usual, wood stone coal etc., played for about 3 or 4 hours mining and such. got to around 300 and 150 something, and the the world stopped rendering in. animals were frozen in place on the edge of the rendered areas. i waited a good 15 or so minutes, watching youtube a bit but it never loaded. i changed render distances, ran along the edge a good ways, but no progress. i hit 'save and quit' then went to do laundry, came back bout 30 minutes later and it was still saving my game. i force closed the app on the nin.  switch and got the game error message. i opened the game back up and my world was deleted. i didn't  know how to file this bug because i have no idea  if it is just one bug or not. sorry for the jumble.