His elbow is affecting his jumpshot. He's been missing plenty of jumpers he knocks down in his sleep. He's been getting hacked down low in the paint too and not getting calls which had compounded that.
The lack of assists are because OKC has a damn good defense that's making it tough on all the role players.
All the main option players in this series have struggled to be consistent on offense (Jokic, Jamal, Shai and Jdub), so it's not just isolated to him.