I jumped into my nether portal, and as it was teleporting me in a baby zombie killed me. I tried to click the respawn button, but it was greyed out. The title screen button was greyed out as well. I was on multiplayer LAN so my friend smashed the portal, and I could respawn. This was in the latest snapshot, 21w19a. We had keepinvetory set to "true". I was tipped over on my side, as if I had died, but I wouldn't disappear. When my friend used his sword on me it made the " attack" noise. Similar to hitting someone in creative mode. The hitbox was upright though.