Are you sure that wasn't the algorithm making it's multiple passovers to better position the labels? Under the default settings and 200 labels it takes a while

Are you sure that wasn't the algorithm making it's multiple passovers to better position the labels? Under the default settings and 200 labels it takes a while to finish positioning the labels. Try changing the Max. Round and Algorithm values to 1 and see if it still flickers/moves as you experienced before.