After applying ITMS 7.1 SP2 MP1 rollup version 5, AD Imports of distribution groups will not complete. Prior to applying rollup version 5, imports of distribution groups were subject to a limit of 1500 resources -- similar to the issue documented in TECH206298 for Security Groups.
No errors are present in the logs. With trace logging enabled, the following trace log entries quickly fill the a.log:
Date: 6/14/2013 11:35:15 PM
Tick Count: 11628688
Host Name: SMPServer
Process: AeXSvc (1532)
Thread ID: 39
Description: Fetching range (member;range=15898086-15899084) - with filter: (&(objectCategory=group)(groupType:1.2.840.1135184.108.40.2064:=2147483648)(distinguishedName=CN=GroupA,OU=Test1,DC=EPM,DC=local))
Issue is resolved as of ITMS 7.1 SP2 MP1 Rollup Version 6. See rollup release notes.
SMP 7.1 SP2 MP1 Rollup Version 5