Belly mower Rck60B on outer to blades are not engaging

[Theduck]

Help, mowing this morning noticed odd cut, stop checked belt, blades all looked good. Lifted and noticed the outer two blades on belly mower are not engaging. Any ideas thoughts, thank you in advance

 

[whitetiger]

The pulley below the gearbox is loose on the output shaft and has sheared the feather key.