This is a bug :(
We reproduced it and managed to fix it. The fix will be available in the upcoming Q4 release (scheduled for the 20th of December). As a matter of fact the problem was not related to positioning the handle correctly but rather to refreshing its position when the Minimum or Maximum property changes.
You could use the following work-around until we release Q4:
After setting the Minimum and Maximum properties you could change the Value property to some integer and then set it back to the desired value.
e.g.trackbar.Mimimum = -50;
trackbar.Maximum = 50;
trackbar.Value = -1;
trackbar.Value = 0;
I'm sorry for the inconvenience.