I have a variety of shapes - circles, rectangles - with centre points marked with 0.25pt lines. This actually represent drill holes for a panel so are precisely positioned. If I ‘group’ all items for the panel, I can set bounds by manually typing in new co-ordinates and shift them all to a new position on the page.
If I “undo” the set bounds, the shapes move back to their original position (actually, I’m not sure about this now - they may not be based on a recent test) but the lines only move near-abouts! I then have to go back through each one, re-positioning to their proper (original) location.
If I click and drag the group to a new position, then everything moves. If I click and drag back, everything moves. This approach keeps everything in place but is not so precise.
In terms of shifting things around, Omnigraffle is not calculating positions correctly for lines except with drag and drop.