cluster service on MS 2012 OS

Dear Experts,

may I please have your opinion on this and help to resolve an issue I have.

is it compulsory to have MS failover cluster running with a specific service account?  If yes, could please explain why? OR why it is suggested to run with a created service account?
my current file cluster service on 2012 OS is running as local system.  I created my file server cluster with my admin account which is member of domain admins. As this is UAT platform I only noticed a warning message today.  ( my admin account is not service account for any service)

I checked the eventview and noticed below error

https://technet.microsoft.com/en-us/library/cc727283(v=ws.10).aspx

my error code 49 and solution in the article is as below:

Error code 49 (Invalid credentials)

This error code might indicate that the user's password expired while the user is still logged on the computer.

To correct invalid credentials:
1.Change the user's password.
2.Lock/unlock the workstation.
3.Check if there are any system services running as the user account.
4.Verify the password in service configuration is correct for the user account

my concern is with number "3"  ??

did I miss something with during cluster creation regards to service account?
regards

Kuzum