Lava Rivers and Lakes + Caves = Invalid state lava on spawn (levitating lava)
Played around with the world settings. I raised the ore heights, but more importantly, I had tweaked the Y noise of the level and enabled lava water bodies (and raised their frequency by a lot as well).
When I spawned in, I found a lava cave with invalid state lava. Also, there were a lot of lighting glitches in that very cave, however, I don't know if that is relevant. See screenshots.