variable is always constant inside class (but not if accessed from outside)

An interesting problem for which I'm running out of ideas to solve;

The function 'LiftStepperRun' first updates the measurement result 'resultAndStdDev',
and then compares this with a constant 'setForce'.

I can read the measurement result from outside the class. This reacts as expected.
But inside the class, if I do the comparison, 'resultAndStdDev.sum' always seems to be stuck at 1277952. (I determined that value by changing 'setForce')
This when at the same time 'resultAndStdDev.sum' changes every second to a value around 992138.

public strainGauge::resultPlusDeviation resultAndStdDev   //resultAndStdDev.sum varies here

public void LiftStepperRun()
{
	nonBlockMeasure();   //this function updates 'resultAndStdDev.sum'

	if ((resultAndStdDev.sum) > (setForce))   //resultAndStdDev.sum is here a constant
	{
		tone(3, A4, 15);
	}
}

We're not Snippets R Us. Please make a compilable example of what you try to do. This just shows nothing.

I just solved my problem :).
My solution files got corrupted somehow, I deleted them all and recompiled.
This problem puzzled me for several days..
I agree it's difficult to come to this solution based on my question, but this forum seems a bit too stressfull for me.