A fake death screen shows up if you have equipped an item that brings your maximum hp dowm to 5 hearts, then get poisoned. Afterwards you can see the death animation in F5 and the inventory.
There is no death message in chat, and you look normal for other players. Relogging fixes the problem.
Steps to Reproduce:
1. Use an item that lowers your maximum hp. (At least -10hp/ -50%)
2. get poisoned.
3. After clicking respawn everything is normal, except you're in a death animation.