Subsurface is missing its base surface, it cannot be drawn
Quite often after model is open, even if all previous simulations were ok, the message from the title appears. It gives us the number of subsurface(s), but as soon as they are not drawn we cannot delete them manually. Exporting to idf and importing the model back produces a lot of other errors and changes some names (e.g. for thermostats). So, it is not a proper way. How to cope with this suddenly missing subsurfaces? And why does it happen?