I have added a few new fields for a defect. But these fields are appearing sometimes whereas other times it disappears. Why is this happening? And how can it be fixed?

If you're using RQM 3.x, then defect handling has been moved to the RTC application and your best first prospect for forum response would be https://jazz.net/forums/viewforum.php?f=1

If you're using RQM 2.x, then you'll need to provide more information about version, browser and context within the application. You might be best to go the route of a formal support request thru http://www.ibm.com/support/servicerequest/