My first guess is you don’t actually have 6 wavelengths the first time you run the script.  At some point you are either calling SYSP 201, 6 after trying to set the 6th wavelength or you are manually enabling the 6th wavelength after running the script the first time.  Then, when you run the script a second time, there is already a 6th wavelength so the SYSP 202, 6, 0.43 sets the 6th wavelength correctly.  Can you confirm that you have a SYSP 201, 6 before calling SYSP 202, 6, 0.43.

If the order of ZPL commands isn’t the issue, can you please share your complete code?

Hi MichaelIH,

Thanks so much for the quick reply. You’re right, I only had 5 wavelengths in my system and I didn’t call SYSP 201, 6 until later. I thought by calling SYSP 202,6, 0.43 it will automatically add the specified wavelength. Now it’s fixed, thanks again for the quick fix!