There's a strange problem in Multiplayer

When I joined in my friend's world,I found I had nothing in my backpack.I had joined in this world several times and I'd had some tools in my backpack. I thought I'd died.However,when I left the world and joined in the world later,I found my things back.It's really strange.It's like I have two accounts in that world,but I actually have one account.My account is always logged in.

Now,when I join in that world,I will be in the account that has nothing.I have to join in the world again to find my original account back.I hope the bug will be debugged soon.(Perhaps there's something wrong with my grammar cause I'm poor at English😂)