Hello Enrico, I am not involved in packaging python3-magics++, just tried to reproduce this fault.
Unfortunately it did not show up in my minimal test VM. It produced a png with a frame and a text and a symbol at the bottom. Is there something more expected to be in the rendered png? Do I have missed to install some kind of map data or similar? You write grib_dump shows no fault, should XyGrib work on that file too - it shows me (translated): file cannot be opened. It's not a GRIB file or it contains no valid data or ... Might that give a hint on what is the issue? Maybe you could add a backtrace of the assert? Kind regards, Bernhard
