Heard a thumping sound when running

Unplugged the dryer from the wall. Removed the back bracket holding the top on. Then the top will slide back and lift off. Next I removed the screws holding the control panel. Removed the door. Removed all the screws holding the front cover on. Removed the lent shoot. Manually rotated the tumbler. Checked both rollers in the front. Found one with the flat spot in it. Removed and replaced it.