Keys Method - Holding [ALT] while pressing twice the same key
IF there is an additional window that comes up, potentially masking the window that you're interacting against, that is exactly the expected behavior. Unexpected window triggers when an action is attempted but there is another window that comes up.
If there is no need to specifically send these keystrokes to the specific window, you could simply send the Keys action to Sys.Desktop. That will simply interact with the desktop itself.
Alternatlvely, you could attempt to use LLPlayer.KeyDown and LLPlayer.KeyUp to simulate the desired actions.