---
title: "Fixing Schedule Build Failures"
url: https://phatdev.net/en/docs/sl-migrations/how-to-resolve-schedule-build-failures
lang: en
updated: 2026-10-20
alternate:
  vi: https://phatdev.net/docs/sl-migrations/how-to-resolve-schedule-build-failures
markdown: https://phatdev.net/en/docs/sl-migrations/how-to-resolve-schedule-build-failures.md
---

# Fixing Schedule Build Failures

Part of the doc set: [SL Migrations](https://phatdev.net/en/docs/sl-migrations.md)

> The backup schedule does not run, or runs and then fails silently.

## Schedule Build Failures

## The schedule does not run at all

### 1. WP-Cron does not fire

The plugin relies on WP-Cron to run schedules. If WP-Cron does not fire (the site has no traffic and there is no system cron), the schedule will not trigger.

**Fix**: set up a system cron - see [Schedule backups](https://phatdev.net/en/docs/sl-migrations/schedule-backup).

### 2. The schedule is disabled

Go to **SL Migrations → Schedules** → check whether the schedule is active. If it is paused or disabled → turn it back on.

### 3. The plugin is not active

It sounds obvious, but sometimes you deactivate the plugin and forget to reactivate it after an update.

## The schedule runs but fails

### 1. Memory limit / timeout

WordPress's cron context usually has a lower `max_execution_time` than a web request. A build needs a longer time.

**Fix**:
- Set up a separate system cron with a higher `max_execution_time`
- Or raise the global `max_execution_time` in php.ini

### 2. Storage write fails

Check the log of the failed package. In **SL Migrations → Packages**, click the package with status `Failed` → read the log to see which phase failed and why.

Common causes:
- Permission denied → [Fixing permissions](https://phatdev.net/en/docs/sl-migrations/how-to-fix-file-permissions-issues)
- Disk full
- Database error → [Database write issues](https://phatdev.net/en/docs/sl-migrations/how-to-fix-database-write-issues)

### 3. The previous build is stuck

The plugin has a lock to prevent two builds from running at once. If the previous build crashed, the lock may remain → a new build cannot start.

**Fix**: wait a few minutes, or delete the lock file manually (the `slm_pro_lock.bin` file in the plugin folder).

### 4. Cloud storage unreachable

The schedule uploads to remote storage (SFTP/FTP) - if there is a network or credentials problem, the local build is fine but the upload fails.

**Fix**: go to **Storage** → click **Test Connection** to verify. Update the credentials if needed.

## See also

- [Schedule backups](https://phatdev.net/en/docs/sl-migrations/schedule-backup)
- [Builds that get stuck](https://phatdev.net/en/docs/sl-migrations/how-to-resolve-builds-getting-stuck-at-a-certain-point)