User Profile Synchronization service stuck in "Starting" state in SharePoint 2013

We know its hard to define what cause the user profile synchronization service not getting started as there are plenty of reasons due to dependency when it dosnt start and might need a SharePoint log analysis to come to any conclusion. I was working on such a scenario where the user profile synchronization service was not getting started at customer environment and following was the exception from ULS when it failed.

02/19/2016 15:16:21.79 OWSTIMER.EXE (0x259C) 0x2D04 SharePoint Portal Server User Profiles 9sip High UserProfileApplication.SynchronizeMIIS: Failed to configure MIIS post database, will attempt during next rerun. Exception: System.Runtime.InteropServices.SEHException (0x80004005): External component has thrown an exception. at Microsoft.Office.Server.UserProfiles.Synchronization.ILMPostSetupConfiguration.ConfigureMiisStage2() at Microsoft.Office.Server.Administration.UserProfileApplication.SetupSynchronizationService(ProfileSynchronizationServiceInstance profileSyncInstance). eadf609d-1937-f04a-6fd0-052797a13efb

The exception seems to be pointing to the custom PowerShell profile and I have learnt from customer that they configured custom PowerShell profile previously which they later removed. So to eliminate any chance of custom profile role in this issue, I had to rename\backup of the windows profile for the timer service account which we use to start the UPS. As you know it should be done by logging in to server using a different account and again login to server using the timer service account so that it will create a new and clean profile. This time the User Profile Synchronization service started like a champ. 

Happy SharePointing!!!