alignment

I have an INFURIATING problem. Sometimes after constraining a bunch of simple rectangular extruded parts into a box, the whole thing has gone out of alignment with the workspace axes. See the "measure" screenshot - that whole rear panel is perfectly constrained to all the other components but...

Centering bushes as used for bolster plate alignment on mould tools. Not to be confused with guide bushes that form the guide pillar and bush set.