dual screen - window slides beneath default panel

[52ROSt]

LM 17.3, 64 bit, KDE

I connected a second screen to the docking base of my note book. It works nice except for one point.

On the main screen I have my default panel on the left edge of the screen. Now, with the second screen connected, a window, which is maximized slips under the default panel at the left edge. This is bothering because it covers important icons etc of the maximized window of many applications.

When I remove the note book from the docking base, thus run it as a standalone with only the internal screen, all maximized application windows do NOT slide under the default panel.

I am grateful for help on how to solve this problem!