User Sync:can't synchronization all the users

User Sync:can't synchronization all the users

Hi,I have two sites need synchronization all users(about 2400 members), form a master site(wp3.9.2) to a sub site(wp4.1),all of them with buddpress and no multisite.
when I begin synchronization everything looks good,but always stop synchronization when finish about 1200 members.

the log is like this:

[2015-01-13 03:22:27][S] 01 - new subsite conection - central_url=http://www.xxx.org;; replace_user=0;; overwrite_user=0;;***
[2015-01-13 03:22:27][S] 02 - sending request - url=http://www.xxx.org/wp-admin/admin-ajax.php?action=user_sync_api;;***
[2015-01-13 03:22:28][S] 03 - sending request - response=ok;;***
[2015-01-13 03:22:28][S] 01_2 - sync users for new subsite***
[2015-01-13 03:22:28][S] 02 - sending request - url=http://www.xxx.org/wp-admin/admin-ajax.php?action=user_sync_api;;***
[2015-01-13 03:22:29][S] 0-10 - ajax actions***
[2015-01-13 03:22:29][S] 0-10 - ajax actions***
[2015-01-13 03:22:29][S] 4-10 - hash sum error***
[2015-01-13 03:22:29][S] 3-10 - p or hash not set***
...
[2015-01-13 03:48:45][S] 0-10 - ajax actions***
[2015-01-13 03:48:45][S] 5-10 - start sync_user***
[2015-01-13 03:48:45][S] 15 - insert user - step 1***
[2015-01-13 03:48:45][S] 17 - insert user - step 2***
[2015-01-13 03:48:45][S] 18 - insert user - ok***
[2015-01-13 03:48:46][S] 0-10 - ajax actions***
[2015-01-13 03:48:46][S] 4-10 - hash sum error***
[2015-01-13 03:48:46][S] 3-10 - p or hash not set***
[2015-01-13 03:48:46][S] 0-10 - ajax actions***
[2015-01-13 03:48:46][S] 4-10 - hash sum error***
[2015-01-13 03:48:46][S] 3-10 - p or hash not set***

can you hlep me?