Hi @arminunruh ! Thanks for your answer. I changed the height to 40 px and it works with the default icons but still not with my custom icons (The arrow is on the right position, the x not).
Unfortunately the thin red bar is a indispensable part of the corporate design of my company, so I could not afford it to make it thicker : )
But ... I tried menu Style 3 and it worked! Even with the thin red bar and the custom icons. A mystery!
Thanks for your help, guys!