While analyzing instances, I have seen cases where the nodes/slave/ directory contains many agents but the config.xml could not be found. This results in many files `nodes/slave/<slaveName>/config.xml` containing the exception:
--- WARNING: Could not attach <JENKINS_HOME>/nodes/<agentName>/config.xml as it cannot currently be found ---
java.io.FileNotFoundException: File '<JENKINS_HOME>/nodes/<agentName>/config.xml' does not exist
at org.apache.commons.io.FileUtils.openInputStream(FileUtils.java:292)
at org.apache.commons.io.FileUtils.readFileToString(FileUtils.java:1765)
at org.apache.commons.io.FileUtils.readFileToString(FileUtils.java:1800)
at com.cloudbees.jenkins.support.configfiles.SecretHandler.findSecrets(SecretHandler.java:96)
at com.cloudbees.jenkins.support.configfiles.XmlRedactedSecretFileContent.getInputStream(XmlRedactedSecretFileContent.java:25)
at com.cloudbees.jenkins.support.api.FileContent.writeTo(FileContent.java:85)
at com.cloudbees.jenkins.support.SupportPlugin.writeBundle(SupportPlugin.java:316)
at com.cloudbees.jenkins.support.SupportPlugin.writeBundle(SupportPlugin.java:278)
at com.cloudbees.jenkins.support.SupportPlugin$PeriodicWorkImpl.lambda$doRun$0(SupportPlugin.java:820)
at java.lang.Thread.run(Unknown Source)
[...]