4.5-year-old SB 8200 - intermittent issue and suggestion to buy new product.

Modems don’t tend to slowly go bad. They either work, or they don’t because they aren’t manageming much. AKA they aren’t a router. 

When things like this start dropping, I start checking the lines. Got a screensnip of the cable connections age and event logs? 

Ok, I performed the event log search as suggested. 34 channels appeared in the Downstream Bonded Channel section. 32 of the 34 channels were locked, the 2 that were unlocked had 0db SNR/MER, and only 3 of the 34 were under 30db SNR/MER, the other 31 were all over 30db. The Power levels on all 34 were within the range of -15 dBmV to +15 dBmV.  On the Upstream Bonded Channel section only 1 channel came up and it was had a Power level of 50.8 dBmV.  I followed the instructions to the T from the Arris FAQs Consumer Care page on SB 8200 Cable Signal Levels. To be honest, I have no idea what all these numbers mean, and I don’t need to, I pulled them up and provided them for the experts on this community forum so hopefully one of you will be able to guide me to my next step. My modem has been going in and out of connectivity again all evening, I’m actually sending this reply via my phone’s hotspot because my modem will not stay operational, 4 lights lit, 2 blue, 2 green, long enough for me to send this. 

What I really need to know is:

1. Is my modem functioning properly based on the numbers above?
2. If so, what else do I need to do to test my system to get it to perform at a standard level? My router system is a TP Link Deco 2A80 Mesh with 3 pods.
3. If my modem is crapping out, what should I replace it with? Is the SB 8200 still the best 3.1 for coaxial internet service?

Thank you in advance for any help/guidance you can provide me with...thx

You need a screensnip of the numbers and event logs. Just saying “that doesn’t help much because there’s a certain range between all of them, there’s errors that need to be viewd, and the logs that help check long term reports. 

In terms of testing, your best bet for checking speeds is to hardwire a pc to the modem and check its speeds. While the SB8200 has 2x ethernet ports, only 1 device can be connected to it for most ISP’s. So disconnect the router, reboot the modem, and wire your pc to it for speed testing. That ensures its not a slowdown on the router side causing issues. 

For the Deco, there isn’t that model. Do you mean the X80? 

In terms of modems, checking on cox’s approved list would be advised. Xfinity’s been moving on to next gen/midsplit speeds. Not sure what cox’s direction is with that so you’d need to check with them/their forums. 

Correction, mesh is 

TP-Link Deco Mesh AC1900 WiFi System (Deco S4) – Up to 5,500 Sq.ft. Coverage, Replaces WiFi Router and Extender, Gigabit Ports

I really appreciate your support, let me know what else I can send to assist you with trouble shooting my issue...

As ​@plemans  suggested, please connect a computer directly to the SB8200 modem to isolate the issue and monitor the connection for 24 hours. Check if the internet connection still drops, and also see if the modem reboots on its own when the connection drops. Please check if there is a splitter on the coaxial connection. 

I will do as you suggest, however my laptop doesn't have an ethernet port so I need to order an adapter. Also, there is no Splitter in the Coaxial line and most of the time the modem does reboot on its own, but not always.

Your power levels are all over the place, you have a ton of errors in the line, and the log is indicating line issues. 

Start with removing any amplifiers, signal attenuators, or splitters from the coax.
From there check the line for kinks, damage, moisture in the line.
Check the connectors for improperly made ends, foil touching the copper coax line, loose connections, bad/old/cheap connectors, or corroded connections. Replace them if you do.
If you can, simply connect the modem right where the coax comes into the home. This prevents wiring in the home from being the issue. And some ISP’s charge if the wiring issue is in the home. So this helps prevent this.

If you’ve done everything for checking the line that I’ve suggested prior, then the ISP needs to check it. 

Thank you, I have 1 long line from the point of entry to the modem, I will check the 2 connectors and see how it goes...thx again

Update:

I ordered a new modem, a Humax HGD310 - DOCSIS 3.1, although Cox website stated it was compatible, and product description stated it was compatible, it didn't work...Cox worked 45 minutes on trying to get it functional...I finally gave up, put my SB8200 back in place and it has worked flawlessly since. Whatever Cox did to get the Humax cleared through, it flushed out whatever was causing the SB8200 to randomly drop…

With that said, I don't know what the cause of the random drops were or what was done to clear it, but it's done, and I want to thank everyone, especially Plemans for the generous time and effort contributed to my issue...