I still don't fully understand what happened.

Somehow the value in the zOffsetA channel was different to the value in the 'origin' line. It seems probable that one version of Poser was reading the value for the origin from the 'origin' line, and the other version was reading it from the zOffsetA channel.

The question remains why the value in the zOffsetA channel was different. It seems to be related to the fact that I had used the "Animatable Origin" switch in the Properties tab at some stage. Turning the switch off again later did not resolve the problem. I was stuck with a rogue value in the channel. Interestingly it was only the OffsetA channel that was wrong, the OffsetB channel held the correct value (the inverse of the value in the 'origin' line).

It seems so blindingly obvious in hindsight, but I had not realised that the enabling the "Animatable Origin" switch set 'static  0' in the channel. Of course the very name of the switch tells you that it does just that, but I must have been  having a Homer Simpson moment.

:blushing: