User management problem

I have a problem with the FBA solution, when I create new external users it works fine, and the full name and email address are correctly displayed. Five minutes after that it updates the user and deletes the email address and Full name, I don't know why. Our solutions requires both fields to be completed since the next process requires to notify the users.

The solution worked fine for a couple of weeks, then this problem appeared. I was using FBA 1.3.1 and then upgrade to 1.3.5 and the problem is still there.

I will update with any future details. Any help or comments are welcome.

My guess is that you have 'My Sites' setup, and the My Sites profile information is overwriting the profile information on your site (and My Sites doesn't have the user's email address or full name).
Hi thank you for your quick response. Unfortunately, in this case we don't have My sites setup in use. We found a problem with User Profile Sync Service, apparently is not working. Do you think it must be working and could this affect the solution with our problem?
Thank you very much, I really appreciate your help.
That would be my guess is the profile sync is happening and overwriting the profiles. Try disabling the profile sync scheduled jobs and see if the values stop being overwritten.