Iphone drops call after 10-15 minutes on SURFboard DOCSIS® 3.1 FW.IPv6 FORWARD drop

If this intermittent issue is happening only on WIFI connected device with both the WIFI network that is 2.4 and 5G then we  would suggest you to try changing WIFI channels will avoid interference and that will give better speed and connection. If other Wi-Fi sources such as neighboring wireless access points are using the same wireless channel, this may cause intermittent connectivity issues, even if the competing signal is relatively weak.  Changing the wireless channel within the  gateway can improve connectivity.

After changing WIFI channel as recommended on the link restart the modem then we would request you to monitor the connection for next 24hrs.

That did not work.

I am now using ONLY WiFi and not cellular and it still happens. The only thing I see in the even logs 

Thanks for sharing the information. 

Please contact your ISP (Internet Service Provider) as they monitor the event logs. 

If your Event Log is reporting a high volume of errors, this would indicate a potential CMTS signal issue. To troubleshoot these errors, we would like to note the current signal levels being used by your Modem.

Share the cable signal levels by clicking the link below:

http://arris.force.com/consumers/articles/General_FAQs/G34-G36-Cable-Signal-Levels