It is hard to answer this without images of you looking straight ahead relaxed, then raising your eyebrows and getting angry and frowning.
I will try to answer you question since i have a over 40 years experience with this and learned from the dr who invented it in canada before it was approved in the USA.
when botox is given in the forehead and not enough is given in the correct areas in the brows,eyelid drooping may occur or asymmetry of the brows.
In addition when you cant make any motion in the forehead, you will try to compensate by using other muscles,so when you try to express anger, all your effort will be in the left brow now creating a wrinkle.This is due to in adequate dosing or placement is given in the brows. It I often see this with patients treated at "botox parties" where all patients are treated identically with no examination or individualization of the therapy. NO TWO PATIENTS ARE ALIKE AND MUSCLE STRENGTH NEEDS TO BE EVALUATED INDIVIDUALLY. YOU MAY TELL AN INEXPERIENCED INJECTOR IF THAT DO NOT TAKE PICTURES PRIOR TO INJECTION AND ON THE REVISIT.