gotoAndPlay("menu"); gives a TypeError

programming flash
1

From a frame named “menu”, I click a button which takes me to a frame named “lesson”, when I click a button on the lesson-frame named “less_btnabort” I want to be taken back to the “menu” frame, but when this is about to happen, I get this error:

TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at flags_fla::MainTimeline/flags_fla::__setProp_btn_editor_Scene1_actions_layout_6()
    at flags_fla::MainTimeline/flags_fla::frame6()

So the “menu” frame doesn’t show up completely. Just some of the buttons on that frame show (but the label simply set as “Label”). And none of the actions on that frame starts to happen.

I’m not sure at all about what’s wrong…
Doing the same thing from the menu but to a frame named “options” and back to the menu-frame works fine.