A further remediation you may wish to try is to rebuild the index from scratch. This process takes a bit more time and is a bit more invasive than the incremental build above.
Basically, you want to shut down Confluence and remove the <confluence_home>/index directory. Then bring Confluence back up and trigger the index rebuild task as outlined above.
This should completely rebuild your index and ensure that future incremental indexing tasks succeed as expected.
Hallo awake hey
The cause of this problem is that the Confluence index has stopped working for some reason. You'll need to restart the indexing process.
This page in the documentation may help:
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