**Affected version:** 8.2 - 8.5.2
**Fixed in:** 8.5.3

### Problem Description

The problem applies to transforms that use more than 1 CCS cluster or 1 local and 1 CCS as source. A typical source could look like this (the important part: `remotes*`):

```
        "index" : [
          "remotes*:filebeat*"
        ],

```

If 2 indices share the same name the transform might fail with an error similar to this:

```
 Failed to retrieve checkpoint due to: Duplicate key logs-2022-11-14 (attempted merging values [... and ...]
```

Similar to the above the `_stats` call is broken for such a transform, it can fail with an error message starting with:

```
Failure during checkpoint retrieval
```

This can happen even if the transform is in state `STOPPED` or `FAILED`.

### Mitigation

Choose _one_ of the following mitigations:

 - split your transforms to use max 1 CCS/local indices

_or_

 - avoid upgrading to 8.2, until the issue got resolved (this is a regression of #80984)

_or_

 - avoid duplicate names for your indices even on remote cluster, e.g. name the index: `remote1-filebeat...`, `remote2-filebeat...`


### Solution

This is a regression of #80984 which introduced a new way of check-pointing. The remote needs to be prefixed to the index name.
x-pack/plugin/transform/src/main/java/org/elasticsearch/xpack/transform/checkpoint/DefaultCheckpointProvider.java
* @param newSourceIndexes the set of indexes seen in the new checkpoint
     */
    void reportSourceIndexChanges(final Set<String> lastSourceIndexes, final Set<String> newSourceIndexes) {
        
        if (newSourceIndexes.isEmpty() && lastSourceIndexes.isEmpty() == false) {
            String message = "Source did not resolve to any open indexes";
            logger.warn("[{}] {}", transformConfig.getId(), message);
            transformAuditor.warning(transformConfig.getId(), message);
        } else {
            Set<String> removedIndexes = Sets.difference(lastSourceIndexes, newSourceIndexes);
            Set<String> addedIndexes = Sets.difference(newSourceIndexes, lastSourceIndexes);
            if (removedIndexes.size() + addedIndexes.size() > AUDIT_CONCRETED_SOURCE_INDEX_CHANGES) {
                String message = "Source index resolve found more than "
                    + AUDIT_CONCRETED_SOURCE_INDEX_CHANGES
                    + " changes, ["
                    + removedIndexes.size()
                    + "] removed indexes, ["
                    + addedIndexes.size()
                    + "] new indexes";
                logger.debug("[{}] {}", transformConfig.getId(), message);
                transformAuditor.info(transformConfig.getId(), message);
            } else if (removedIndexes.size() + addedIndexes.size() > 0) {
                String message = "Source index resolve found changes, removedIndexes: " + removedIndexes + ", new indexes: " + addedIndexes;
                logger.debug("[{}] {}", transformConfig.getId(), message);
                transformAuditor.info(transformConfig.getId(), message);
            }
        }
    }
}