We are using Pega 7.1.8. We didn't find any error in logs but when I checked the index file (DesignerStudio > System > Settings > Search (Check)) it was showing error "Work index file unavailable or corrupted".
So we decided to re-index and check once. After re-indexing search was working fine.
Wonderful. Looks like the problem is solved. If this happens in future, it would be great to have the logs from the node when this work object changed but did not get indexed. You might also want to check the table pr_sys_queue_ftsindex to see if an entry was left over for this change and did not get processed to update the index.
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