Hotkey wont work if its modifier is also being used as part of the trigger - windows

Question

This issue seems to only occur in this one program.
I have the hotkey Shift+a set in this programs hotkey editor dialog, I want to trigger it in AHK using Rshift and w;
RShift & w::
SendInput, +{a}
Return
For the life of me, it will not work. I press Rshift and w and nothing happens at all. Triggering the hotkey manually by pressing shift and a works just fine.
The strange thing is the following works:
LCtrl & w::
SendInput, +{a}
Return
So does this:
w::
SendInput, +{a}
Return
I also tried to send Rshift back up before triggering the hotkey, no luck:
RShift & w::
SendInput, {RShift up}
SendInput, +{a}
Return
Is there a rule that says you cant use the same modifier as the target hotkey in the trigger that I missed?
please dont suggest that I use other modifier keys, shift +[key] is all that I have left.
Any help would be greatly appreciated!

Answer 1

Firstly, you shouldn't use a custom hotkey combination when a modifier exists (unless you have a good reason to):
For standard modifier keys, normal hotkeys typically work as well or better than "custom" combinations. For example, <+s:: is recommended over LShift & s::.
And secondly you shouldn't escape keys in a Send(docs) command that don't need escaping:
Enclosing a plain ASCII letter (a-z or A-Z) in braces forces it to be sent as the corresponding virtual keycode, even if the character does not exist on the current keyboard layout. In other words, Send a produces the letter "a" while Send {a} may or may not produce "a", depending on the keyboard layout. For details, see the remarks below.
And then about the problem itself:
I of course can't know if this will work, but I'd simply try the following:
>+w::a
This would work because because the remapping syntax actually uses the blind sendmode.
Alternatively, you could, of course, just manually use the blind sendmode:
>+w::SendInput, {Blind}a