Raised it with QlikTech. Got Below Response.
The Admin is using "loop field in document" but the field in document has more than 1800 Access Control Entries (ACE), trouble applying permissions may occur. Less than 1800 entries will work fine.
Windows has a limitation to assign more than 1820 ACEs or if the ACL exceeds the size of 64K.
There should be an error in Windows Event Viewer "You have exceeded the operating system's limit on the number of users and groups that can be in a security information structure. Remove some users or groups and try the operation again."
QlikView will run with no error, however, and the ACE permission will not be establish correctly.
Workaround is to have less than 1800 ACE or ACL size less than 64K.
MS article: http://support.microsoft.com/kb/166348
So if we try to distribute a particular user document to more than 1800 users at a time, the file will not be distributed to accesspoint. However, task will run fine saying document is successfully distributed. But the user document will not be visible in accesspoint.
The reason I am saying user document is , suppose a source document is reduced by Country field which has India and China, and India has 1500 users and CHINA has 2000 users. Then QMC task will show that document is succcessfully to both countries. But in accesspoint, only INDIA file will be visible. CHINA will not be visible as it has more than 1800 users.