Possible Bug in Section Print Flux and Anisotropic Materials

Hi all,
I am using Calculix 2.20 and ran into an error when running a heat transfer simulation and trying to record the heat flux through a defined surface. If I use an ORTHO solid material and add the line:
*SECTION PRINT, SURFACE=surface1, NAME=nsurface

I get the error “*ERROR in materialdata_cond conductivity for fluids must be isotropic”, even though there are no fluids in my simulation file. If I make the solid material isotropic, the simulation runs fine. However, I need to have anisotropic materials for my simulations and need the heat flux through a defined surface.

Any advice on how to fix this issue would be greatly appreciated, thanks!

What if you remove that line - does it work ?

Can you share the input file for tests ?