I did all of the steps to create the adjustable part and just now tried using the minimum distance to measure between the shoulder screws instead of the linked sketch circles. When measuring the minimum distance between the shoulder screws, I get 1.633". When measuring between the linked sketch circles created from the shoulder screws, I get 1.632. It's only .001, but that's enough to cause the axial constraint to fail when I use the 1.633 distance in the variable table.
That's another puzzler since the sketch circles are driven by the shoulder screws and they should be exactly the same.
There does seem to be an update issue and we are checking this out.
I've looked at the case and sometimes it updates like you would expect and sometimes not.
As pointed out earlier the Measurement variable can be used for many cases like this. I also use PMI dimensions for this as shown in the video which I think will give you what you want.
In the video the PMI dimension shown is the variable that is driving the length of the spring and is fixed to measurement plane.