1996 Oldsmobile Bravada windshield wipers

My wipers work at all settings and the washers also work. The issue is when they are on any intermentent setting and come down to the bottom of the window they go down below the glass and then come back up and stop at the bottom of the windshield before going into the next cycle. Also when the wipers are on low or high speed they also go down below the bottom of the glass but do not hesitate before going back up, then when the wipers are turned off they go down below the glass and then back up to the bottom of the windshield and stop. Whats up?