This behavior is by design. See the first point on the fixed section of the changelog for 1.0.9: https://docs.unity3d.com/Packages/com.unity.behavior%401.0/changelog/CHANGELOG.html#fixed-4
> Node execution will no longer be deferred to the next frame. This means an entire graph can fully execute in a single frame if none of its nodes take time to execute. Because this can potentially allow users create an infinite loop using a Repeat node or Start with repeat on, we will now abort a graph and throw an exception if it takes longer than a second to run in a single frame. Note: This abort will not happen if the debugger is currently attached to the process.
You can add a "wait frame" node in between to achieve the desired behavior.