Having a duplicate hotkey is a user error. Simple logic dictates this. When a is pressed, which one should the program call, the top or the bottom one? If it should call both, in what order? that isn't defined, any more than using two labels that are the same.
Code:
a::
;something
return
a::
;something
return
;or
;...
something
gosub label
return
Label:
;do something
return
Label:
;Do something entirely different
return
As for the keyboard layout missing, check your spelling, recently i had something like that and i was missing an r.
Code:
ScollLock:: ;Not on keyboard
ScrollLock:: ;will work.