R6700 dropping internet - amber/orange light on internet light

A few weeks ago my internet connection has started to drop periodically (10-12 times per day, sometimes hours between, sometimes within 20-30 minutes, no clear pattern). Connection is usually out for 2-3 minutes then back up. As it's an intermittent drop I've had a hard time narrowing down the issue since it pops up and random intervals and self corrects - but it's still a full drop of wireless and hard wired connections (including VOIP phone for work so it's not an issue I can simply work around). When out the internet indications on the modem all appear normal, the router internet light is amber/orange and the remaining lights are as usual.

Issue began 2 weeks ago with no apparent cause - no hardware or service changes, the same setup has worked great for over 2 years.

Cox ISP - TM3042 Modem - R6700v3 router running wifi and hardwired connections (firmware version 1.0.4.106)

Attempted fixes to this point:

- Multiple calls with ISP, remote resets and remote support. They can't see an issue (or don't know what to look for).

- hard reset on the router (via reset pin on back)

- ISP has replaced modem (no change)