Windows 10 + multiple layouts switcher

[popobawa]

Problem:
I use 3 keyboard layouts in my Windows 10 laptop: English, Russian and Japanese. I use ru and en very often, and only from time to time I use jp, so I've decided to the following: set Capslock to cycle through ru and en and set win-j to call jp layout.
To do so I wrote copy-pasted the following code I found here on the forum:

Code: Select all

; Clever layout changer
; Define lang constats
ru := DllCall("LoadKeyboardLayout", "Str", "00000419", "Int", 1)
en := DllCall("LoadKeyboardLayout", "Str", "00000409", "Int", 1)
jp := DllCall("LoadKeyboardLayout", "Str", "00000411", "Int", 1)

Capslock::
w := DllCall("GetForegroundWindow")
pid := DllCall("GetWindowThreadProcessId", "UInt", w, "Ptr", 0)
l := DllCall("GetKeyboardLayout", "UInt", pid)
if (l = en)
{
    PostMessage 0x50, 0, 0x4190419,, A
}
else
{
    PostMessage 0x50, 0, 0x4090409,, A
}
return

; set japanese
#j::
PostMessage 0x50, 0, 0x4110411,, A
return

And it works of a sort! It worked perfectly well in windows 8.1. It still works in windows 10 but here comes the problem: not in every window. Let's say it does not work in windows store window. No idea why. It doesn not work in Run window (that thing appearing after win-r). It does not work when UAC asks me for admin password if I need to run something with admin rights.
What is more interesting, is the fact that all other Autohotkey hotkeys work perfectly well in the windows specifed above. So I guess - just guessing - that the problem is with this PostMessage thing.
Anyone faced this issue? Any clues?

PS Running the sxript with admin rights does not fix this, I've tried to do it.