I have this same issue. Were you able to figure out the cause of the inconsistent readings? Mine vary by as much as 3dKH between successive readings. What is the expected range of deviation between measurements of the same sample? I just did 3 back to back measurements, and got results of 6.6, 8.5, and 7.3.

Another thing I'm finding is that if you start a measurement manually, the results are not stored in the history. Is it supposed to work that way?