When your timing is off and you're pushing the ball instead of throwing the ball, there will be a decrease in velocity. If the timing is off or the arm slot is off, you won't see the same thing.
His (left) elbow is lower than it should be and he's not pitching like he's coming off a slope. At times, his arm was where it was supposed to be ... but his inconsistency with his arm slot is what leads him to throwing pitches that no major-league hitter would swing at.
I didn't see a dead arm. I saw some pitches with a lot of life and a lot of movement. The problem was that Oliver didn't do that consistently. Until he gets a consistent arm slot, he's going to continue to struggle to throw strikes.
You don't want to get too overly involved in velocity at this point. You want to give him a chance to stretch his arm out.