Good to know. Would you agree with my instructor that I should stay at the same weight and increase reps? Or do you think it's not really much of a problem and I should go back to 3x5 and increase weight.
I would probably increase reps until you start to become more stable because you definitely don't want to have that issue when the 5 reps become hard with heavier weight. Try to also hit those stabilizers in your back with pull ups and rear delt flys. I think flat dumbbell presses would also help out your stabilizers.