uitableview - xcode 6: puzzling tableview cell constraints -

my app has number of tableviews. each cell has textview , switch. cannot constraints behave consistently. in many cases height of table view cell 98 , height of textview 90 , y=8. if attempt update constraints, wants set both bottom , top spaces 8 , other times not. wants adjust height of textview. have been unable see pattern. set cell height text height + 8. frustrating because want of text views align consistently. doing wrong? or bug?

try set 4 constraints textview

top space bottom space leading space (left)

all 3 parent view (the cell) , height constraint