Logic Error 20 in gxhpng. Notify Developer

[Patrick Reuter]

Dear GraDS developers,

I print netcdf files in Grads 2 with the command printim (GD compiled
etc.), and I get the following error message in 30 out of 45 tested
frames :

Logic Error 20 in gxhpng.  Notify Developer

And the png (or even gif) is not created.

Could you please help out ?

Thanks in advance
   Patrick