I think this may be caused by your incorrect training posture, and the weak side movements are out of shape, which leads to uneven muscle training. Compare the upper and lower parts of both pectoralis major muscles to see if they are the same. If not, practice the weak side and pay attention to the upper or lower part of pectoralis major.
I suggest you pay attention to your movements in future training, don't use too much weight, reduce the weight of the stronger side appropriately when going up or down, and pay as much attention to the weaker side as possible.
Some personal thoughts, I hope they are useful to you.