Hi Robbe,
I am afraid that I am not able to reproduce the issue of incorrect resizing behaviour of the form or user control when the width of the docked control is adjusted with the attached sample.
Could you please modify the sample so that the issue could be seen clearly? Also please provide a video file showing the issue. This will help us to resolve the issue soon.
http://websamples.syncfusion.com/samples/Tools.Windows/F61883/Main.htmBest regards,
Golda