Alias names are missing while assigning to user

Hello Experts,

I am facing one problem in my BOBJ system frequently. During user creation via CMC console of our BOBJ system, we used to assign alias name. So, while assigning alias names, sometime it shows list of available alias names and sometimes it disapeears. And after sometimes , it is visible again in list. We are not able to understand what is causing this condition in our system.

Thanks & Regards,

SJ