After upgrading Spectrum to version 20.2 the oneclick tomcat remains "running" for approximately two minutes and then it shuts down.
Error seen in tomcat (stdout.log for Windows or catalina.out for Linux)
SEVERE: Failed to create server shutdown socket on address [localhost] and port  (base port  and offset )
java.net.BindException: Address already in use: JVM_Bind
OneClick Tomcat won't startup due to java.net.BindException exception because default shutdown port, i.e. TCP/8005 was being used by other process.
DX NetOps Spectrum
The shutdown port provides a neutral and scriptable way for the operating system to shut down a Tomcat instance. For http or https port, no application can use the same port. If you have multiple tomcat processes running that use the same shutdown port, you will need to configure one to use a different shutdown port.
For DX NetOps Spectrum OneClick, the shutdown port is configured in the $ SPECROOT/tomcat/conf/server.xml file and by default is 8005.
You can edit this file and change it to use a different port for example, 8006 or 8007.