Input fields in panels

Hi,
we are developping currently an application for the stone industry based on BricsCad V21 Pro. We use the .net api. I face the problem that input fields in a panel are disabled / read-only. I have to add that we create our controls in WPF, not in windows forms. Buttons and list-boxes are working correct.

Is there anybody with experience in WPF / BricsCad panels?

Thanks in advance.