I’m using Font Creator Professional Edition 12.0.0.2567
I was testing the glyph Ć̣ in the opentype designer to set the anchors correctly for mark to base attachment and I get an error “argument out of range.”
I didn’t know whether I had the glyph Cdotbelow with acute but pasted that onto the preview bar and then immediately I got the error “argument out of range.”
I was able to quickly leave the opentype editor.
I close the opentype designer and was afraid to lose my progress so I saved the font file. I can use and edit the font but I am unable to open the opentype designer due to “argument out of range.”
We no longer maintain that version, as we do not have enough resources. We have fixed numerous issues over the last years, so upgrading should solve the problem.
Maybe you have a specific preview text that is causing the issue. Can you open the OpenType Designer with another font, and then change the preview text. Then try to open this font?