Not an instructor here but a former student. If your stroke is flawed it can keep you from improving past a certain point. When I went to my first lesson I was an underhandicapped APA 4 or 5 in a very strong area but hit a wall. After watching me shoot, the instructor told me that my timing being so good was the only reason I was able to run 3 balls. My cue was only on line during the moment of contact with the CB. If anything was off even a little I would miss. Until I straightened out my stroke I would never achieve any level of consistency. If you know your stroke is flawed, tear it apart and fix it. I couldn't run 3 balls for about a month after starting the lessons but once the new stroke began to take I improved very quickly. After nine months of lessons and drills to groove my new stroke I went from being the worst guy at the pool hall to being in the mix at the top. The funny thing was I didn't know my stroke was bad at all. I booked the lesson to work on my 9 ball break. After watching me shoot, the instructor told me he was not going to help me break the balls better since I couldn't run out anyway. A better break would only make it easier for me opponents to run out on me.
Just my .02
Good luck!
Just my .02
Good luck!