Your problem is the result of the outer jacket being too short for the inner cable. Assuming you have an OEM cable there are only two things can cause that problem: Either the adjuster is missing(they will fall out of the grip assembly or slip off the end of the cable when the cable is removed) or the "timing" marks on the internal gears in the grip are misaligned. This, together with drag in the cable due to fraying, dirt or a kink will cause the problem you're seeing.
That is all I have to offer. Take it for what it's worth. Like many others here, I only have about 50 years of riding, wrenching and racing on motorcycles. I still ride about 15,000 miles a year and currently own and service 3 K bikes. I will admit that since I don't hack up good machines I probably don't know as much as you.
Now, on behalf of the members here, please go away.