Remember why you do drills in the first place --- and that is to improve your skills when you are playing an actual game. Some shots during a game allow for a slight margin for error, like pocketing a ball in a wide pocket with no obstructions, for example. That margin for error will also apply for bank and kick shots going into that same pocket. So your drill shot would probably be fine in those cases.
But you may have some issues with shots requiring precise tip placement and stroking, like for example, where you have very little room for the cb to pass an ob on it's way to the ball you want to pocket, or if you have to thread a needle with the cb to get position on the next shot.
Diagnosing the problem when you're almost perfect in that drill is a little tricky. When it's that close, I doubt that it's caused by unwanted sidespin. Even the slightest amount of sidespin can easily cause the cb to miss your tip completely on the way back, depending on speed. I think you should check your stance and angle. You may be shooting at your target at a very slight angle without realizing it.
