In the current implementation, the thermal conductivity is not updated for the basal flux boundary condition. Thus, erroneous results will be produced when temperatures in the model exceed the adiabat and the thermal conductivity is updated to the asthenosphere value. This should be handled somehow, though the general idea would be that using the flux boundary condition would generally be for crustal models where the adiabatic temperatures should never be reached.
In the current implementation, the thermal conductivity is not updated for the basal flux boundary condition. Thus, erroneous results will be produced when temperatures in the model exceed the adiabat and the thermal conductivity is updated to the asthenosphere value. This should be handled somehow, though the general idea would be that using the flux boundary condition would generally be for crustal models where the adiabatic temperatures should never be reached.