Using SAML on the APM Workstation Webstart is not working in versions 10.5.2.0 and later as well as 10.5.1 Hotfix #24 and later.
A change was made to the workstation.jnlp file to accommodate 'Sun Java deployment rule set' based on location. An href location was added to the file and inadvertently broke the functionality of the SAML security mechanism.
To restore the proper functionality of SAML, remove what is below from line 10 in <APM INSTALL DIRECTORY>/product/enterprisemanager/plugins/com.wily.introscope.workstation.webstart_10.5.1/WebContent/jnlp/workstation.jsp. This change is effective immediately and does not require any restarts or cache clearing.