I have been upgrading the asterisk version from 13 to 16 on FreePBX 14 systems using the asterisk-version-switch command. After the upgrade, several of the customers are reporting intermittent issues with picking up parked calls and having agents not being able to pause/unpause in the queues. It usually occurs once or twice a week and lasts around 10 to 15 minutes and returns back to normal. I can see that AGI calls(parkfetch.agi,queue_devstate.agi) are taking a long time to execute and are returning the value 4.
I have moved some customers back to asterisk 13 and they no longer have the issues.
I am looking for suggestions on how to troubleshoot this.