So, you think that your mechanics change enough on high inside shots that they cause you to miss? You seem to be very stuck on this one particular shot, but this makes no sense to me. Your mechanics are your mechanics...either they are shite and they affect every shot or they aren't and they aren't the reason you miss.
If your stroke, etc is changing literally because you are hitting high inside, you don't have any fundamentals and you need to tear your whole game down and learn from the ground up, quite literally from the ground up.
Good luck
They are currently shite, as you say, and affect every shot, but not in any consistent way. But they seem to be much more pronounced on the combined-English shot. It's a matter of degree, not black & white. Yes, I probably need to tear alot down. My stroke has been on the darkside for years.