滚动视图的UIlabel换行符如果时间太长则无法正确显示（iphone视网膜模拟器）

i have UIlabel using below code, i don't know maybe its too long or not. but when it is scrolled, the uilabel get this result. How can i solve the problem? are there any limitation using uilabel?i have UIlabel using below code, i don't know m