S35705423 # Client - Incoming Issues (raised by Client) #Error: "A value for UserName already exists"

fix issue :
Steps:
Use Apply URL to apply for Job 001 ... complete whole process
Use email ingest to apply for Job 002
Change the alias email address to the email address I used for the Apply URL application
Use the password I used on first application ... then click Submit get this error Do you know what that means ? ("value for Candidate")