Funnel Tracking Reveals 0% Trial Activation Bug in PageBolt

We Shipped Funnel Tracking and Immediately Found a Bug Hiding in Plain Sight

PageBolt implemented event tracking for their signup funnel to monitor user conversion. The data immediately revealed a catastrophic 0% trial activation rate despite 546 users reaching the plan selection stage.

Why This Matters

Technical observability often focuses on system errors and performance, yet logical bugs can exist that throw no exceptions. In this case, automated testing and error monitoring failed to detect a hardcoded redirect that silently broke the conversion path, demonstrating that system health metrics are insufficient without business logic funnel visibility.

Key Insights

• Funnel data showed a cliff where 546 users selected a plan but zero activated trials, indicating a logic bug rather than a conversion issue.
• The root cause was a legacy development script in signup.html that hardcoded a redirect to the pricing page, preventing users from reaching the activation endpoint.
• Standard automated testing failed to catch the error because the specific redirect was not included in the existing test flow.
• Error monitoring tools remained silent because the redirect was technically successful and triggered no server-side or client-side exceptions.
• Immediate post-fix results yielded 12 trial activations and 2 new subscriptions within 30 minutes of deploying the code removal.

Working Examples

The funnel query used to identify the 0% conversion rate.

SELECT event, COUNT(DISTINCT user_id) as users, ROUND(100.0 * COUNT(DISTINCT user_id) / (SELECT COUNT(DISTINCT user_id) FROM events WHERE event = 'signup_started' AND created_at > NOW() - INTERVAL '7 days'), 1) as conversion_pct FROM events WHERE created_at > NOW() - INTERVAL '7 days' GROUP BY event ORDER BY created_at DESC;

The hardcoded redirect bug found in signup.html.

<script> window.location = 'https://pagebolt.dev/pricing'; </script>

Practical Applications

• Multi-step flow monitoring: Implement event tracking for onboarding and checkout to detect silent logical failures that logs miss.
• Logic verification pitfall: Avoid relying solely on unit tests and error monitoring, as they fail to capture ‘successful’ but incorrect user redirects.

References:

• https://dev.to/custodiaadmin/we-shipped-funnel-tracking-and-immediately-found-a-bug-hiding-in-plain-sight-kk6