Even after closing the Fiddler application, the instance of the process is still running and when I try to start Fiddler a second time, it shows prompt telling Fiddler is already running and do you want to start fiddler any way. If we choose Yes, then it will give another prompt telling port is in use and shall use random port. This issue is coming only after upgrading the Fiddler to the latest version from the site 4.6.3. Older versions were fine.