Shoulder pain with commencement

I had a previous shoulder injury, and because of that my left shoulder is weaker than the right. Even when I’m applying the 70% rule, my shoulder bursitis flares up. I don’t know whether this is because of the repetitive movement of raising the shoulder while doing the “peng” movement in commencement. I have followed the lessons up to single whip in beginners online series. Most of the days, when I try to practice, after head to toe scan, I tried to do the commencement several times atleast 8 to 10 sets, so that I started getting some kind of resistance-feeling (might be the chi feeling). Will that repetitive movement cause any strain for the shoulder?
Thank you and appreciate any help, Till