Calls dropping after being put on hold after 3 minutes

We are experiencing calls being dropped after 3 minutes. The extension can not pick the call back up and it then disconnects. This is happening on all type of phones Grandstream, Polycom, etc. this seems to be a global issue. Is there an on hold timer that I can change or I have missed? Thanks in advance for your responses.

Asterisk imposes no time limit on hold.

The default time limit for Park is 45 seconds.

Thanks for you response so quickly. Do you have any ideas what could be going on? We are a hosted platform with clients on all ISP’s all type of handsets (including my office) experiencing this. I have proven it on my desk. This is a head scratcher.

The only conceivably relevant timeout is rtpholdtimeout, but that is five minutes, by default, and would indicate something is blocking rtcp.

Maybe a firewall is deleting a dynamic entry after 3 minutes.