Might try setting dimassoc to 2.
How we explain it in generic terms to the guys here:
Dimassoc = 0 : Dimensions are just a collection of lines and text, that happen to line op as extension lines and arrows.
Dimassoc = 1 : Dimensions are smarter, single objects, that if you stretch the nodes, the numbers update. These are independent of any other objects in the drawing.
Dimassoc = 2 : (This is also the setting under Tools -> Options -> User Preferences -> "Make new dimensions associative") Dimensions are smart enough to know what they are tied to. If you dimension a line endpoint to endpoint, it remembers what it is. If you trim the line, the dimension knows to stretch to the new endpoint. (This is the setting, where, if you list it, it says associative yes)
Good points and bad points to Dimassoc 1 and 2, and depends on company standards and preference.
I have never run across many good points for dimassoc = 0, and recommend against it, unless there is a very good reason to use it, and even then, I think twice about it.