DNS keeps resetting to 127.0.0.1 in Windows 10

Step-1: Open CMD and run the below command to see what's the process ID(PID) is open on port number 53. 

netstat -ano | find ":53"

C:\>netstat -nao | find ":53"

  UDP    0.0.0.0:5353           *:*                                    2840

  UDP    0.0.0.0:5353           *:*                                    11464

  UDP    0.0.0.0:5355           *:*                                    2840

  UDP    127.0.0.1:5355           *:*                                6840

Step-2: Open the task manager > processes tab and add the PID column to the display process ID(PID). 

Step-3: Then find the process with process ID "6840" is running.

Step-4: Select the process> right-click on it > click End task.

Step-6: Select the process> right-click on it > click open file location or properties.

Step-7: After finding the location, remove those files from program files. Reboot the PC.

N.B. When you find out the application which is running the process "6840" and if you are able to uninstall it then uninstall it. You can also perform full pc scans by Malwarebytes.