Over the years there have been a lot of postings about this problem. It looks like there may be multiple causes. Looking at some sip debug traces it seems clear to me that it is sometimes caused by a flakey pstn line and a sensitive SPA3102 trying to decide if the call was answered by a device on the line external to the SPA3102. In other words a SPA3102 monitoring the line voltage and current then deciding that the call was answered external to the SPA and discarding any caller id associated with the call. Then the SPA3102 senses more ringing and starts ringing a new call without any caller id. At least that is my theory. I am not aware of the solution.
Network Address Translation (NAT) Settings for Lines on PAP2T and SPA3102 Phone Adapters
The objective of this document is to configure Network Address Translation (NAT) settings for the lines of communication on the PAP2T ...
Speed Dial Settings on SPA100 Series
Speed Dial Buttons are often used to make the process of calling regularly used contacts quicker and with one button. This option is used in place of dialing the entire phone number in. ...
Firmware Upgrade on SPA112 and SPA122
To upgrade the firmware a specific file must be downloaded from the Internet and uploaded to the device. Upgrading your devices can be very useful. Firmware upgrades can fix software bu...