I have encountered this bug in both Chisel (See github.com/TheCricket/Chisel-2/issues/#238) and my personal mod SC2 - in the bounding box method somehow the TileHidden is overwriting other tile entities. It needs further investigation, which I have been attempting myself.

Unfortunately, if that is true, its a bug in Forge. Make sure you have the latest version of Forge.

The reason I say this is that the code that places the heat blocks explicitly checks for normal vanilla Air before placing anything.

Ok.