I have been complaining about this in a very inarticulate way for a while, but finally figured out a repeatable example. In the attached, just move either the magenta line in layout space or the green square in model space and you will see one of the dimensions fly off in space.
DimBug.3dm (86.1 KB)
The one side of the dimension that flies off is snapped to the layout space object, the other end of the dimension was snapped to the model space object. The side that flies off will go to the layout space coordinates that match the model space coordinates that it was snapped over.
I tend to set sheets up so that I have a detail showing a clipped model, and will draw as needed in layout space to augment the model (section lines, hatches, hidden lines, that kind of thing), so this is a situation that I run into a fair amount.