PROBLEM SOLVED EVERYONE
it turns out i didn't dig deep enough into the layers of parts used to compose the drawer boxes . For instance, the groups that comprised the middle drawer box component, dbox_2 (the left and right members, the front and back members, and the bottom), contained references to the top drawer box component, dbox_1. As soon as I changed all the "dbox_1" references to "dbox_2," the middle drawer box started resizing according to overall cabinet depth as it should. Obviously the same worked for the bottom drawer box, dbox_3. as you might have guessed, the reason the groups that comprise dbox_2 and dbox_3 had references to dbox_1 is b/c I created the middle and bottom drawer boxes by making copies of the top drawer box, dbox_1.