Change old files from my/min to mm/sec

With your CO2 device profile open, go to ‘File’ > ‘Settings’ and select ‘mm/sec’
This setting is stored with individual device profiles, so the units will switch automatically when you switch profiles.

I have never heard this behavior reported before. Please do the following - in your CO2 profile, create a new shape/layer with arbitrary settings, and verify that you have units set to mm/sec in your Settings window, and that they are displaying properly in the Cuts/Layers window.

Next open an older project saved from a diode profile. Do the units displayed switch automatically at this point? If you go into your LightBurn settings, is mm/min now selected, instead of mm/sec?

Please send us a few screenshots of this process as you go through it - one of your Cuts/Layers window and Settings window with the new layer/shape, and another of the Cuts/Layers window and Settings window after you’ve loaded a project saved from your diode profile.