For some reason it seems that putting ending brackets on a line messes up vertical justification: Dorico adds a whole lot of space above the lines with endings. I’ve taken care of the usual things in Setup:Layout Options.
Can you attach the project here, please? Or if you’re not willing to attach it, please email it to me at d dot spreadbury at steinberg dot de with a link to this forum thread so I can remember what I’m supposed to be looking at.