I have a theory about the error.
The code uses ‘1.0"’ as the default [one inch in text format].
In the set up for the dialog it uses .to_l to convert it to a length in current units.
So for a user like the author [or me] it works - because
'1.0"'.to_l returns a ‘length’ object e.g.
BUT if the user has a computer where the . [full-stop] is NOT the decimal point but a , [comma] is used, then the .to_l fails because the text version is not convertible to a ‘length’ as it’s expecting a comma.
This decimal-separator is a common set up in much of Europe and some other areas…
However, the fix for this is quite easy - edit the code setting up the defaults to avoid using any decimal-separators in the text versions at all.
dict['p_rad'] = '1.0"' to
dict['p_rad'] = '1"'
dict['h_dia'] = '0.0"’ to
dict['h_dia'] = '0"'
dict['k_width'] = '0.0"' to
dict['k_width'] = '0"'
dict['thick'] = '0.0"' to
dict['thick'] = '0"'
It will then work on either ‘.’ or ‘,’ decimal-separator computers…