I have found after my last save, the Datum Planes of the assembly have just lengthened in two directions monstrously for no reason. I checked to see if it was an unassebled straggler but cant find anything. Is there a way of knowing why it does this.
Check attached image, the dot is a machine 20 metres high and the datum plane seems to reach the nearest neighbourhood for some reason.
.... They were set to Automatic update. I found the problem though, I took the constraints off a suspect part and it was a tangent constraint throwing out the planes. All great now.
You live and learn!!