This anomaly does not seem to be limited to the file mode. I just checked John’s coefficients and the resulting fit posted above and they do not seem to agree either (The residuals are around 3-4 Angstrom)
I’ve no idea what is going on either but the coefficients in the GO window do not seem to be the correct ones to give a good calibration fit so presumably would not work if transferred manually to the dispersion window.
I also went back to v5.4.1 and this does not transfer the coefficients to the dispersion window automatically when using the ALPY 600 balmer line mode either
All very strange