## The problem
Incremental syncs from MongoDB to Postgres kept failing with `java.lang.IllegalArgumentException: Saved offset is not valid`. The sync would then retry from a full refresh, which was expensive on a large collection. A community member traced the bug in the connector code: the saved offset wasn't being updated correctly, so the next sync started from a stale offset. The fix shipped in source-mongodb-v2 v2.0.4, announced by an Airbyte contributor on the thread. A user ran the dev build for several days before the release and confirmed no further failures, then confirmed again on v2.0.4.
## The fix
The connector had a bug where it didn't update the saved offset properly, so every incremental sync after the first choked on a stale offset and fell back to a full refresh. This was fixed in source-mongodb-v2 v2.0.4. Fix: upgrade the MongoDB source connector to v2.0.4 (or later) in your connection settings. Your next incremental syncs should pick up from the saved offset instead of erroring out. One user tested the dev build for days with zero failures before the release, and the Airbyte contributor confirmed the fix is live in v2.0.4.