https://github.com/ptrbortolotti/SONATA/blob/50b6794c31ac736c0282b1db9606ea6bced96139/SONATA/utl/converter_WT.py#L416-L420
These lines calculate the thickness of the shear web parallel to the chord line. If the web is not perpendicular to the chord line, then the actual web will end up thinner than intended.
Open pull request https://github.com/ptrbortolotti/SONATA/pull/14 addresses the fact that these lines incorrectly double shear web thickness, but does not currently address the measurement being parallel to chord line.