Event Tracking Broken (core event stopped firing), Mixpanel

Event Tracking Broken (core event stopped firing) for Mixpanel stores. Tracked live in Vortex IQ Nerve Centre. How to read it, why it matters, and how to act on it.

Metrics type: Key Metrics • Category: Nerve Centre

At a glance

Event Tracking Broken (core event stopped firing) is a real-time alert that fires the moment a named core event (for example Purchase, Add to Cart, or Begin Checkout) records zero occurrences for longer than an hour during normal trading. Unlike a percentage drop, this is a hard signal: a core event going completely silent almost always means the tag was removed, renamed, or broken in a deploy. Because so many funnels and metrics depend on these events, a single broken one can quietly corrupt a whole dashboard.

What it counts	The count of designated core events over a rolling one-hour window. The alert latches when any core event reads zero for more than an hour while the store is active.
Sample type	Backend API data from Mixpanel event counts, evaluated in real time per core event.
Why it matters	A silent core event breaks the funnels, cohorts, and conversion rates built on it. Catching it within the hour stops days of bad data accumulating.
Reading the value	The card lists each core event that has gone silent, with the time it last fired. Each open row is a tracking incident to investigate.
Currency	count
Time window	RT
Alert trigger	core event count = 0 for >1h
Sentiment key	mix_alert_tracking_broken
Roles	owner, marketing

Calculation

Vortex IQ watches the count of each event you have marked as core. If any one of them records zero events across a rolling one-hour window during normal trading hours, the alert latches for that event. The check is per event, so one silent event raises a flag even while every other event keeps flowing. The one-hour window filters out the natural gaps that a low-volume store can have overnight.

Worked example

A representative reading of Event Tracking Broken (core event stopped firing) for a typical merchant on Mixpanel. Say a theme update on 14 Jun 26 renames the checkout button handler, so the Begin Checkout event stops being sent. Within the hour the card flags Begin Checkout with a last-seen timestamp of 09:12. Add to Cart and Purchase are still firing, which tells you the break is isolated to one step. You confirm in Mixpanel that the event count flatlined at zero, hand the timestamp and event name to engineering, and they trace it straight to the renamed handler. Because the funnel built on that step now looks collapsed, you also expect the funnel-conversion-drop alert to be open. For deeper investigation, use Vortex Mind to trace upstream causes; for natural-language exploration, ask Ask Viq.

Sibling cards merchants should reference together

Card	Why merchants reach for it
mix_core_events_firing	The live status board for every core event, the natural place to confirm the break.
mix_alert_event_volume_drop	Tells you whether the break is one event or a broader ingestion collapse.
mix_alert_conversion_drop	A silent funnel step usually triggers this conversion alert at the same time.
mix_health_score	Summarises overall tracking health so you can see the blast radius at a glance.
mix_ingestion_lag	Rules out delayed ingestion as the reason an event looks like zero.

Reconciling against Mixpanel

Where to look in Mixpanel’s own dashboard:

Open Insights, select the named core event, and view it over the last 24 hours grouped by hour. A genuine break shows a clean flatline at zero from a specific hour. If you see a small but non-zero count, the event is not fully broken and the cause may be a partial deploy or a single platform (web vs app) losing the tag.

Why the Vortex IQ value may legitimately differ:

Reason	Direction	What to do
Ingestion lag. Batched SDK events can arrive late and look like a gap.	Apparent zero that later backfills	Check the ingestion-lag card before declaring a break.
Event renamed. The event still fires under a new name, so the old name reads zero.	True zero on the old name	Search Mixpanel for a similarly named new event.
Quiet hours. Genuinely low-traffic windows can produce real zeros overnight.	Expected zero	Confirm the alert respects trading hours for your store.

Cross-connector reconciliation: if your ecommerce platform still records orders while Purchase reads zero in Mixpanel, the event tag is broken, not the checkout. For divergence investigations, use Vortex Mind.

Known limitations / merchant FAQs

Q: How often does Event Tracking Broken (core event stopped firing) update? It evaluates in real time on a rolling one-hour window, so a silent core event surfaces within roughly an hour of the last successful fire, plus any ingestion lag.

Q: The event is firing on web but the alert says it stopped. Why? The alert looks at total volume for the event. If one platform (often mobile app) lost the tag while web kept it, total volume may still dip to zero in a low-traffic hour, or the break may be platform-specific. Break the event down by platform to confirm.

Q: We renamed an event on purpose. Will this keep alerting? Yes, until the core-event definition is updated to the new name. Point the core-event configuration at the new event name so the alert tracks the right thing.

Q: Can I customise the alert threshold? Yes, the silence window and the list of which events count as core are configurable per profile in the Alert Rules tab. Add the events that matter most to your funnel and tune the window to your traffic pattern.

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Tracked live in Vortex IQ Nerve Centre

Event Tracking Broken (core event stopped firing) is one of hundreds of KPI pulses Vortex IQ tracks across Mixpanel and 70+ other ecommerce connectors. Nerve Centre runs the detection layer; Vortex Mind investigates the cause when something moves; Ask Viq lets you interrogate any number in plain English.

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