# Increased Function Invocation Errors - ERR\_MODULE\_NOT\_FOUND

- Provider: [Vercel](https://down.guide/providers/vercel)
- Confidence: Confirmed
- Impact: Degraded
- lasted 2h 10m
- started 2026-05-18 21:42 UTC
- Vercel states the impact was 2026-05-18 18:15 to 22:16 UTC (4h 1m)
- id: DWN-02ac32f047
- Official page: https://stspg.io/6knpl12q53h5

## Updates from Vercel
### 2026-05-18 21:42 UTC: investigating
We're investigating an issue where customers are currently experiencing application failures due to function invocation errors when using React Router 7.

### 2026-05-18 21:53 UTC: identified
The issue has been identified and a fix is being implemented.

### 2026-05-18 22:11 UTC: identified
We're continuing to work on rolling out a fix. In the mean time, customers may use Instant Rollback to a previous deployment version as an immediate workaround in order to recover.

### 2026-05-18 22:16 UTC: monitoring
A fix is rolled out for the function invocation errors affecting React Router 7 deployments. To recover, redeploy your application or use Instant Rollback to a previous deployment from the dashboard. We're continuing to monitor.

### 2026-05-18 22:19 UTC: monitoring
We are continuing to monitor for any further issues.

### 2026-05-18 23:52 UTC: resolved
This incident has been resolved.
Some deployments created between May 18, 2026, 06:15 PM - 10:16 PM UTC may have experienced increased ERR\_MODULE\_NOT\_FOUND function invocation errors due to a bad rollout. Deployments created outside of this window are unaffected.
The fix is being rolled out to existing deployments retrospectively and is expected to finish in the next few hours.

From the builder: does your app depend on Vercel? [Sazabi](https://www.sazabi.com/?utm_source=down-guide&utm_medium=markdown&utm_content=vercel) detects problems in your own logs without hand-written monitors, and you can ask it in plain language which errors mention Vercel.

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