Hello Dorico team!
When editing the staff spacing by clicking and dragging the blue or red boxes within the Staff Spacing toolbox in Engrave mode, releasing the mouse results in the mm value being edited displayed in the page margin to change slightly. Interestingly, I have only been able to reproduce this with other zoom levels than 100%.
It’s certainly not a very serious bug, only a little annoying, but I’m reporting it anyway in case you did not already know about it.
All the best!