I didn't claimed the phone is broken. I claimed the SPA is generating the ring signal of type not recognized by the phone. E.g. misconfigured SPA.
Well, as you have access to WWW GUI you can reset the unit. At least you can reset other unit, save it's (factory default) configuration into a file then provision the suspicious unit with it. It will result in factory-default configuration of the SPA in question.
Save configuration of a virgin unit (set to factory default) into file. Put such file on tftp, ftp, http server. Configure "Provisioning Rule" option of device with issue - order it to load the saved file. As the saved file is the image of factory default configuration, the suspicious unit should revert to factory default on load of such configuration file.
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