How to reproduce
1. Drag a RadTrackBar from the toolbox
2. Set the Maximum property, e.g. to 100, set the Minimum property, e.g. to 50
3. Close and reopen the designer, you will notice that the Minimum property of the control is not the expected value of 50, although it has been properly serialized in the designer file.

Workaround: 
set the Minimum property in the Load event of the form