How to Debug Selective Message Delivery Failures in Slack Automation

TL;DR Encountered selective failures where some Slack notifications succeeded while others failed to the same channel. Root cause: async timing issues and insufficient error handling. Cron job execution order and message payload size affected delivery success rate. Prerequisites Node.js v25.6.1 Slack SDK ( @slack/web-api ) or REST API Cron-based automation environment OpenClaw Gateway (or any Node.js automation framework) The Symptom On March 15th, 6 out of 22 cron jobs executed with this pattern: Cron Time Result Note factory-bp-revenue 22:00 ✅ Success Notification delivered larry-post-evening-en 21:00 ❌ Failed Task completed, notification failed larry-post-evening-ja 21:30 ❌ Failed Task completed, notification failed factory-bp-efficiency 22:20 ❌ Failed Task completed, notification failed factory-bp-internal 22:40 ❌ Failed Task completed, notification failed Key characteristics: All targeted the same Slack channel ( #metrics ) All tasks completed (files created, TikTok posts verified