WP Smush only optimizes couple images then does not continue


I was using WP Smush Pro earlier on and I have around 200 images smushing before and I had to restart it three times to get all 200 images optimized a week ago.

However, this couple days when I was optimizing around 100 images it always stops after 2 - 3 images. It keeps loading but it does not move for almost 5 hrs. Was wondering was there some changes or why would that be the case?