You encounter the below errors in the Events panel of the default APM UMA Health and UMA Health Cluster dashboards.
DX O2
The issue is related to defect # DE668614. Investigation reveals that the issue is related to an update in Elasticsearch which introduced stricter handling of reserved characters in query_string queries. Specifically, queries using characters such as namespace:(^\|)* or cluster_name:[^\|]* are no longer accepted in their previous format.
Targeted to be fixed in release 26.5.1