Jump animations for humanoid avatars will fail to play on a semi-random basis resulting in the avatar hopping up into the air in the midst of their standing animation.

Examination of the AvatarControllerTemplate in the sdk reveals that the most likely cause is that the transition from the StandingHeight node to the Airbourne node in the Locomotion layer has the HasExitTime checkbox enabled.

This is most likely an error as having this checkbox enabled means the avatar will not transition from their standing/movement animation into their jumping animation unless they are exactly at the end of the animation