If a strong line is not in the catalogue used for fitting (either through simply not being in it, or if excluded using --exclude-line), its residuals will artificially inflate the uncertainty calculated for nearby lines. The approach of excluding the largest two residuals in the 20-unit fitting window is not sufficient. A more careful approach of quantifying the distribution of the residuals may be required.
If a strong line is not in the catalogue used for fitting (either through simply not being in it, or if excluded using --exclude-line), its residuals will artificially inflate the uncertainty calculated for nearby lines. The approach of excluding the largest two residuals in the 20-unit fitting window is not sufficient. A more careful approach of quantifying the distribution of the residuals may be required.