Resize of browser window caused the pull down of bar menu always on top-left corner.

Hi,

I just tried to resize the browser window to very small, and I noticed that the bar menu change it style to something that is for mobile phone (which is good).

But when I resize the browser window back to a normal size, the bar menu get broken. All the pull down of it goes to the top-left corner.

Please refer to the screen 1, 2, and 3 attached.

I am using Windows 10 Pro, IE 11.

Regards,

Felix CHAN