DimOrdinate is acting up in Layouts - when the referenced detail is changed - moved, scaled, or locked - the dimensions change.
The only change in the images below is whether the layout is locked. After the change in dimension value, it does not switch back.
It seems like the basepoint of the ordinate dimension (0,0 in model space) is changed to the origin point of the layout page (0,0 in paper space), but as if that point were in model space.
Any changes to scale in the detail will now reference the basepoint coordinates in Paper space, but translated to Model Space.
Rhino 6 SR5 2018-5-12 (Rhino 6, 6.5.18132.5131, Git hash:master @ b8b8945d46018b7f175f54f1e384ede46df9745d)