Several ability tasks used to apply root motion sources on Characters have ordering problems between on-completion style events and ::EndTask / OnDestroy. UAbilityTask_ApplyRootMotionMoveToForce is a prime example.
In cases where project code/script wants to specify a movement mode during the task (via bSetNewMovementMode & NewMovementMode) and also manipulate the Character's movement mode after the task is complete, we have a timing conflict:
This pattern may also have propagated into internal Epic project code. It would be good to survey them.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-181073 in the post.