Steps to reproduce:

1. Set DockMinWidth="250" in <avalonDockLayout:LayoutAnchorablePane Name="ToolsPane" DockHeight="150"> in MainWindow.xaml in MLibTest.
   
2. Compile it and run without any config files.
3. Dock the "File Stats" pane to the left side.
4. Change the width of "File Stats" pane to minimum.
5. Dock the "Color Picker" pane to the right side of "File Stats" pane.
   As result the "Color Picker" pane becomes invisible (overlapped).
   See the video:
   Video_2019-10-22_152250.zip

Seems like these changes introduced the issue: f7427b7