Why does satellite-sync keeps getting stuck at the message "Freeing read locks for locker ..." ?

Issue

• Why does satellite-sync keeps getting stuck at the message "Freeing read locks" and how to fix it ?

Downloading:######################################## - complete
14:38:04
14:38:04 Downloading rpm packages
14:38:04    Fetching any missing RPMs: rhel-x86_64-server-6 (2900)
14:39:03    Total size: 5.02 GiB
14:44:31       Downloaded 5.01 GiB of 5.02 GiB. Estimated remaining time: 5:17:32
14:44:31     2896/2900 Fetch successful: fence-agents-3.1.5-17.1.el6_3.x86_64.rpm (153920 bytes)
14:44:34       Downloaded 5.02 GiB of 5.02 GiB. Estimated remaining time: 0:11:47
14:44:34     2897/2900 Fetch successful: selinux-policy-targeted-3.7.19-155.el6_3.6.noarch.rpm (2748184 bytes)
14:44:37       Downloaded 5.02 GiB of 5.02 GiB. Estimated remaining time: 0:06:27
14:44:37     2898/2900 Fetch successful: selinux-policy-3.7.19-155.el6_3.6.noarch.rpm (1314680 bytes)
14:44:37       Downloaded 5.02 GiB of 5.02 GiB. Estimated remaining time: 0:02:00
14:44:37     2899/2900 Fetch successful: selinux-policy-minimum-3.7.19-155.el6_3.6.noarch.rpm (2485932 bytes)
14:44:40       Downloaded 5.02 GiB of 5.02 GiB. Estimated remaining time: 0:00:00
14:44:40     2900/2900 Fetch successful: selinux-policy-mls-3.7.19-155.el6_3.6.noarch.rpm (2419448 bytes)
14:44:40 Processing rpm packages complete
14:44:40
14:44:40 Importing package metadata
14:44:40    Importing *relevant* package metadata: rhel-x86_64-server-6 (2900)
            ________________________________________
Importing:  Freeing read locks for locker 0x10: 25537/140379561912064
Freeing read locks for locker 0x12: 25537/140379561912064