Provisioning issue with SPA504G phones

I’ve experienced this problem across two (current) distro installs with multiple phones…

I provision an extension to use a 504G phone. I reset the phone to defaults and reboot it. It loads the config and displays its extension and name, etc. But the phone cannot make calls. Any keypress results in an immediate fast busy.

The solution I stumbled upon by chance is to edit the custom config for the extension and enable the web interface (it is disabled by default). I rebuild the config, but the ‘reboot phone’ command doesn’t work. I have to manually reboot the phone, at which time it picks up the new config THEN executes the reboot command I’d sent from FreePBX. Once this all completes, the phone works as expected.

I’d rather not have to manually edit the config for every phone to get them to work, and I’d rather not leave the web server running on the phone. Is there a fix/workaround for this?