OK, so I just updated to experimental-2.0.384 and since there were a few changes to the MOX system since the last version I was using I rebuilt my MOX generating cluster. It's MOX so I'm running it about as hot as the reactor will possibly go without turning into a big hole in the ground, with all the usual side-effects of things not in HazMat suits bursting into flame and getting radiation poisoning. Oddly, I have never had any problem with anything turning to lava until now. Most things still aren't turning to lava. There's plain old Vanilla stone hanging out just one block away from my reactor doing everything you'd expect solid rock to do.
On the other hand, the bedrock is melting and disappearing leaving a gaping hole into the void. Nothing else, just the bedrock. Is this normal/intentional?