I have seen the problem with form jump around when editing tolerances and stuff. If you are just checking form only as in a flatness I find that I only get good results when the surface is the datum I have as one of my prinmary alignments. If you remeasure you should see a consistant reading as long as you don't start trying to edit things for that feature. If you do need to edit it is best to remeasure that feature.
I have seen the problem with form jump around when editing tolerances and stuff. If you are just checking form only as in a flatness I find that I only get good results when the surface is the datum I have as one of my prinmary alignments. If you remeasure you should see a consistant reading as long as you don't start trying to edit things for that feature. If you do need to edit it is best to remeasure that feature.
