# X_PWA_SYNC_INCOMPLETE

## Means

the background-sync outbox flush left mutations queued

## Typical cause

**registered, thrown by nothing since 21.0.0**, for the same reason as `X_PWA_SYNC_FLUSH_FAILED`: there is no flush endpoint to report `remaining > 0`. A queue left undrained stays in the page's IndexedDB and replays on the next load

## Fix

delete any branch that matches this code, because it never runs. `pwa.backgroundSync` is a **boolean**, and the retry schedule is the browser Background Sync API's own

[PWA and build skew](/error-codes#pwa-and-build-skew)