If you set the number of channels in the Freq sink block > 10 (in my case 11), grc will throw an error.
"if len(labels[i]) == 0:
IndexError: list index out of range"
Upon further investigation, the source code it generates only has 10 arguments in the alphas, colors, widths and labels fields. If I manually edit the source and add an 11th argument to the alphas, colors, widths and labels fields, then run the code from a terminal, it runs no problem. Seems like a GRC only error.
Just wanted to report.
thanks,
-b