Queue doesn't failover - sometime work sometime not

Hi all,
I having a major problem. I’m using Device and user mode.
Currently the problem is, when there is incoming call, the call looping in same queue and didn’t failover to second queue. Its like on and off. Some time its failover and sometime not.

When it didn’t failover, in CLI show as below

2015-09-07 10:50:01] VERBOSE[15499][C-00007320] res_musiconhold.c: – Stopped music on hold on DAHDI/i2/(MY DID HERE)
[2015-09-07 10:50:01] VERBOSE[15499][C-00007320] res_musiconhold.c: – Started music on hold, class ‘SOCMUSIC’, on DAHDI/i2/(MY DID HERE)

I still can listen the music. When the agent paused and I un pause the agent, the call go to unpaused agent again.It should not ring again since agent retry i set as no retry in freepbx. I cracking my head. Please help me experts.

Asterisk Version: Asterisk 11.6-cert6
FreePBX version :