So in normal kit PvP, in the dungeon, there's this lava next to the steps that make you jump, right? Well, I fell in the lava, and after 3 hits it stopped hurting me and I was just sitting there hitting everyone. Here's a screenshot: Also, sometimes, in both kit PvP and blocks vs zombies, my arrow goes down when I aim it up, even when it's fully charged. And that happens like 5 times in a row then.
This is actually not a bug since fall and fire damage is turned off. (And yes that includes Lava) Just do /spawn to get out of it.
That's weird , I tried it on that place to check and everyone was beating the pixels out of me. Also , when you said 3 hits I thought it was Lava damage.