Hi Georgi,
We are extremely sorry for the delay in responding.
I have created a sample and it is working fine. Could you please provide the Essential Suite version currently you are using?
Please make sure you have given the protected modifier for the Base UserControl docking manager. Please take a look at the attached sample which contains the following:
1. UserControl1 is the Base control contains DockingManager and Panel1 with protected modifier.
2. UserControl2 which is Inherited from UserControl1 and it has ListBox with docking enabled.
3. Form1 contains UserControl2.
4. We can see both ListBox and Panel control with docking enabled.
Please let me know if this helps you. Thanks for your patience.
Regards,
Vijay
DockingInherited.zip