Port 8005 is used By Windows 10 System Process

The problems comes from a Windows Service:

https://www.niallbrady.com/2017/02/15/how-can-i-use-express-updates-when-patching-windows-10-with-quality-updates-in-system-center-configuration-manager-current-branch/

Not from another Tomcat instance.

I too was facing the same with windows 10 and ran the command netstat -a -b which showed CmRcService.exe is using the port 8005 on the machine.

The most weird part is sometimes if i hit localhost:8005 in the browser url its asking for username and password to access the page and in the developers tools I cannot see any application name or data whatsoever

Check if port 8005 is really in use by Windows :

Install and run Sysinternals TCPView and Check if the line with "Local Port" 8005 has as "Process" System

Or check the file c:\Windows\CCM\Logs\DeltaDownload.log for port 8005

If the port is in use by system, go to Computer Management and stop the service "SMS Agent Host" or open a command prompt as administrator and type: sc stop CcmExec