My project is using Solr Cloud with Zookeepers. The setup consists of 3 Zookeeper servers and 3 Solr servers. The Solr version is 8.11.2.

A few weeks ago, we had updated the solr schema.xml and added new fields. After uploading the new solr schema, we did restart the Solr service and re-index the Solr collection. We had verified the new Solr schema was working fine.

Last week, we noticed that the Solr indexing was failing. We checked the Solr schema from the Solr admin, and it was showing the new Solr schema. However, upon re-starting Solr services in all 3 Solr servers, the Solr schema was reverted to the previous solr schema.xml (without the new fields that we had added a few weeks ago).

We re-uploaded the latest Solr schema, re-started Solr services in 3 Solr servers and re-index the Solr collection. The Solr indexing was successful and Solr search was working again with the latest changes.

Why Solr schema was reverted to the previous version without any changes? Is it a known issue?