buoyantBoussinesqPimpleFoam creates a random cell as an outlet...
 

I'm making a backward facing step (hot wall) followed by an upside down forward facing step. I am finding that buoyantBoussinesqPimpleFoam makes a single cell on the side of my geometry an outlet. Has anyone had a problem like this before? The case works fine with simpleFoam.

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blockMesh

Is there something wrong with my mesh? I've even made a fluent mesh and imported it with similar results.