It seems that the shoulders are not flat on both sides, but inclined. Wearing suspenders in summer always falls off. Is there any way to flatten shoulders?
Actually, it's good to cut shoulders, but flat shoulders are not necessarily good.
It's easier to do something on the clothes than to flatten the shoulders.
If you must wear suspenders, I saw them sold in Taobao. Add a strap buckle between the two straps at the back, so that you won't fall off because of your narrow shoulders.