Can you attach your *.sldprt file here?
Is the stress really of any consequence?
What you could do is use an iso clipping to show only areas above, below or between values that you define.
If you right click your stress plot and select iso clipping, you can then show only the material that is above the threshold.
you can explode all your parts in the assembly.
then load the stress plots, now you can see the area of the maximum stress.
if you want to know the value you can probe it.