Behavior Tree Service doesn't tick without wait

If I exclude wait, service never ticks. service is supposed to switch enum value within blackboard from “none” to a valid one, and then tree selects right branch based on blackboard condition.

It just occurred to me that perhaps order of execution in each node is determined by order of node elements. service is below selector, so it gets executed after selector is processed. Maybe problem was more of a lack of intuitive understanding on my part instead of a bug?