In non-editor builds UAnimInstance::GetInstanceTransitionTimeElapsed always returns 0.0f.
This is caused within FAnimNode_StateMachine::Update_AnyThread due to:
These wrappings around SourceTransitionIndices were removed in 4.13(CL 3082579) for [Link Removed], however this instance seems to have been missed.
Call UAnimInstance::GetInstanceTransitionTimeElapsed or UAnimInstance::GetInstanceTransitionTimeElapsedFraction in a non-editor build for a valid state machine and transition.
Result: Always returns 0.0f
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-79775 in the post.