I have FF Core configured to display Millimeters in the Region setting, but it ignores it and when I open Impose node settings, everything is displayed in Inches, and there is no option to switch it to mm.
It started happening on both PCs I access it from.
I am not having the problem in FFCore 6.1.6. You could try rebooting the server. Also note that some common press sheet sizes (e.g., 8.5X11 inches) are displayed with inches no matter what the region setting is.