CM1150V Phone quality and connectivity poor after a time.

[bstreyle]

I have a Cable Modem CM1150V which is connected to Comcast (Xfinity).  This modem and phone service has worked well for a long time.  Lately, the phone part of the modem begins to go bad (very poor sound) and then "call failed" on my cell phone that I am using to test my phones at the house.  If you reboot the modem (remove power and wait 30 seconds) the phone works.  Not sure how long it takes for the home phone to begin acting up again.  One time, I woke up and I had no phone service or internet and when I rebooted everything was fine.  Does it sound like my modem is going bad?  Anyone have similar issues?

Thanks,

Bruce

[FURRYe38]

Please post a copy and paste of the modems connection status and event log page.
https://kb.netgear.com/30007/How-do-I-obtain-the-cable-connection-information-from-a-NETGEAR-cable-m...
https://kb.netgear.com/30008/How-do-I-view-or-clear-the-event-logs-on-my-NETGEAR-cable-modem-or-mode...

Be sure your using a good quality LAN cable between the modem and router. CAT6 is recommended. 
What is the brand and model of the host wifi router connected to the modem?

Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.

Have the ISP check the phone signal and line quality UP to the modem. Check all RJ11 phone cable lines and plugs and terminalsBe sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...
https://kb.netgear.com/24311/Power-level-guidelines-for-a-NETGEAR-cable-modem-router?article=24311
https://www.duckware.com/tech/solving-intermittent-cable-modem-issues.html