Incoming caller is muted after being placed on hold

When a customer calls into our asterisk server and is put on hold, there is a chance that when the call is taken off hold the caller will be “muted”. The caller can hear the user talking to them, but the user cannot hear the caller. The staff estimates that a customer will be “muted” 20% of the time if they are on hold for less than a minute, or a 50% chance if they are muted for more than a minute.

I have no idea where to even start diagnosing this; any ideas would be greatly appreciated!

Which channel technology are you using? Enable the protocol logging for that technology.

I’m using SIP. I’m not sure how to be more specific than that; I inherited this server and didn’t receive any training. For what it’s worth I don’t see anything like sip.log in /var/log/asterisk.