Modifier keys state e.g. (Ctrl/Shift/Alt) do not persist across commands

[fishstik]

For example, if I have the following config:

{
    "command": {
        "move-right": "Shift+D"
    }
}

I send the following key sequence:
Shift down,d down,d up,d down

The cursor will move right only once, and will do nothing until I release Shift and send the command again.

[tlhc]

same issue