Hi Alaa,
Thanks for your feedback.
To re-assign the default ABP to affected users, you can refer to the following article to change the user’s ABP as “[No Policy]”.
http://technet.microsoft.com/en-us/library/hh529942(v=exchg.150).aspx
As for the root cause about the issue, I will involve some higher level resources for further investigation. Thanks for your patience.
Thanks,
Claud