Respawn in the air when entering the world and fall to death

The first time I haven’t play one of the worlds for a while, when I opened it I fell from the sky to somewhere near or exactly at the natural spawn point, I respawned and fell again. I tried once or twice but still couldn’t get it right. Then I reopened my world. This time I was finally at the position where I was the last time I left the world normally, but my inventory was empty and my experience was 0, just as if I had died. I hurried to the position where I fell several times from the sky and collected my lost inventories, but I still lost some of my important inventories.

The bugs vexed me a second time more recently after a multiplayer game connection failure. I reopened my world and fell from many blocks above the ground and landed on the natural respawn point, I tapped respawn and respawned at neither my last respawn point nor the natural respawn point.