Per the Oracle DOC ID 1509703.1:
"Managed Server State FAILED_NOT_RESTARTABLE When Class Path Provided And Started From Admin Console (Doc ID 1509703.1)"
After applying the WebLogic Server 10.3.6 PSU, a managed server fails to start when the class path is provided and started from the admin console.
Specifying WL_HOME/server/lib/weblogic_sp.jar;WL_HOME/server/lib/weblogic.jar in the classpath of Server-start is causing this issue. There is no need to set these in the classpath of Server-start since they will come in from the system classpath. If a custom classpath is needed for the managed server. then it should set as below:
The weblogic_patch.jar must precede weblogic_sp.jar and weblogic.jar -- this ensures that the classes in the patch are loaded rather than the unpatched classes.
One weblogic_patch.jar was found on the installation and this was added to the classpath to resolve the problem using this final classpath: