Add known-issue docs for index/alias name clash bug (#92262)

Relates #91456
Relates #91887

Author: DaveCTurner

docs/reference/release-notes/8.5.0.asciidoc

@@ -321,3 +321,13 @@ Packaging::
 * Upgrade bundled JDK to Java 19 {es-pull}90571[#90571]
 
 
+[[known-issues-8.5.0]]
+[float]
+=== Known issues
+
+* It is possible to inadvertently create an alias with the same name as an
+index in version 8.5.0. This action leaves the cluster in an invalid state in
+which several features will not work correctly, and it may not even be possible
+to restart nodes while in this state. Upgrade to 8.5.1 as soon as possible to
+avoid the risk of this occurring ({es-pull}91456[#91456]). If your cluster is
+affected by this issue, upgrade to 8.5.3 to repair it ({es-pull}91887[#91887]).