So that's how you fix that !
I have Harmony One and only for the tv it does that (you hit button only once but it's like you did it fast twice). I hooked up my harmony to pc but couldn't figure out all the delay menus and whatever delay I added didn't change a thing. I didn't know it was in the tv menu that I had to change a setting for this.. I'll try it out, I'm sure it'll work, thx for posting