Hi!
This is why I am thinking it might be those WebRTC and Zulu extensions though, like I said, I would not expect them to actually conflict since they are supposed to have prefixes…
So this is a FreePBX distro, right?
If so, follow the troubleshooting section at the bottom of the wiki page you got the procedure to upgrade (ie create a ticket and upload the logs).
For issues related to the same upgrade, you can keep these together…
There are known DAHDI related issues right now (mostly networking issues though)… What kind of DAHDI hardware do you have?
Someone did report the same problem here
with non-Sangoma and non-Digium hardware…
Good luck and have a nice day!
Nick