Rarely when walking around lava, you will get caught on fire by it. This happens in such a way that the player absolutely should not have been touching the lava. This can also happen with water, in a much less severe way, the air bubble bar shows up for a split second or two.

How to reproduce:
1. Find a nice large lake/lava lake
2. Create some walkways above the water/lava
3. Continue walking around above the water/lava in survival for a while, jumping, running, moving around a lot.
4. Eventually, you will either get set on fire, or notice the bubble bar show up for a second.

This bug can take a while to have happen, i had it happen 3 times in about 10 minutes.

Below you can see some footage of this bug from "N O" (:

This happens on both pc and xbox one, at least.