I'm having the same issues, with exception of crashes which I haven't noticed.
When this happened to me, I had saved the game and then changed texture packs. When I loaded the world again, I spawned in mid-air. When I respawned after being killed, I spawned in the correct place, but lost everything on me when I died.
Issue has been resolved. I added a port fowarding entry for the Switch in my gateway and also defined a static ip for the Switch. After I did that, the Switch now automatically logs into the microsoft account when I start the game. I can also access all my purchased content in the marketplace.