User reports that this issue has been fixed in a recent version: "When I reported this, v 1.0.5 was the newest one (Nov 20), since v 1.0.6 came out Nov 21. Issue is fixed."
On forum:
https://discussions.unity.com/t/behavior-event-channels-not-initialized-when-start-node-is-run-build-only/1556967/8