For some reason, after I play Minecraft for roughly 5 minutes, the corpses stop appearing. Restarting Minecraft doesn't help, but creating a new world does.

I died from TNT, does this permanently destroy the body? Or am I experiencing a bug?

This sounds related to a known issue where the corpse doesn't appear visibly for the player that left it. Things are a bit hectic IRL and it isn't known when things will slow down enough for any of the team to get back to this mod. Sorry.