Drawing only shows last active config volume :(

A have a model with two configurations.

My drawing sheet calls up the volume of my part and displays it in the bottom left corner.

I make a drawing of config A. but it shows the volume of config B

I make a drawing of config B but it shows the volume of config A

WTF?

Eventually I find that all the drawing can do is show the value that comes from the model for the last config that was updated.

It seems the drawing is accessing a variable that is not configurable, but that's not all, its a value that is overwritten with each configuration update.

How strange, and in my case very nearly extremely costly. I have a load of stuff here with costings based on material values that are completely wrong.

Up to now my configs have not had enough difference between them for me to notice what is going on.

SW2016 SP5.0

There must be a work round for this, probably I need to create some global variables or something but so far I cant seem to make anything like that work. I'm down to updating the config in the model and getting a pdf off  my drawing before it goes wrong... ugh!

SolidworksDrawings And Detailing