[CI] MixedClusterEsqlSpecIT test {enrich.EnrichAfterCoordinatorEnrich ASYNC} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic #9465 / 8.14.3_bwc
• elasticsearch-periodic #9458 / 8.14.3_bwc
• elasticsearch-periodic #9444 / 8.14.3_bwc

Reproduction Line:

./gradlew ":x-pack:plugin:esql:qa:server:mixed-cluster:v8.14.3#javaRestTest" -Dtests.class="org.elasticsearch.xpack.esql.qa.mixed.MixedClusterEsqlSpecIT" -Dtests.method="test {enrich.DoubleRemoteEnrich ASYNC}" -Dtests.seed=335E7E4F84CB014 -Dtests.bwc=true -Dtests.locale=es-DO -Dtests.timezone=Asia/Jerusalem -Druntime.java=24

Applicable branches:
8.19

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

org.elasticsearch.client.ResponseException: method [GET], host [http://[::1]:46565], URI [/_query/async/FjVNTlVtQUNaUU9LZDZrRlRCVlJjNVEcQTFYd3dMMTlTdkdMVmpZcjdkTDRVZzoxNjg2Mg==?wait_for_completion_timeout=60s&pretty=true&error_trace=true], status line [HTTP/1.1 500 Internal Server Error]
Warnings: [No limit defined, adding default limit of [1000]]
{
  "error" : {
    "root_cause" : [
      {
        "type" : "illegal_state_exception",
        "reason" : "Found 1 problem\nline 2:3: Plan [EsqlProject[[message{f}#3685, language_code{r}#3679, language_name{r}#3688 AS first_language_name, language_name{r}#3691]]] optimized incorrectly due to missing references [language_name{r}#3688]",
        "stack_trace" : "org.elasticsearch.ElasticsearchException$1: Found 1 problem\nline 2:3: Plan [EsqlProject[[message{f}#3685, language_code{r}#3679, language_name{r}#3688 AS first_language_name, language_name{r}#3691]]] optimized incorrectly due to missing references [language_name{r}#3688]\n\tat org.el
[truncated]

Issue Reasons:

• [8.19] 2 consecutive failures in step 8.14.3_bwc
• [8.19] 3 failures in test test {enrich.EnrichAfterCoordinatorEnrich ASYNC} (5.2% fail rate in 58 executions)
• [8.19] 3 failures in step 8.14.3_bwc (75.0% fail rate in 4 executions)
• [8.19] 3 failures in pipeline elasticsearch-periodic (75.0% fail rate in 4 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)