@Anonym, after a first investigation of the log file, it looks like there is one particular function that is not working properly on your version of the plug-in.
Could you please open an image in GIMP, then open G’MIC-Qt, go to filter Various / Custom Code [Global] , remove the predefined code, and put this instead:
to {``${-gui_layer_pos}}
And tell us what happens.
An expected result is what I have on the following screenshot.
