Downstream light blinking, but gateway status page says "looks fine"

@Barmar Thanks for sharing and posting the pic. It looks well enough. They do go out overtime, and it's hard to tell just looking at it, overall the connections look proper. Have you tested to see if the downstream is lost by directly connecting to the outlet, and bypassing the splitter section? That will stop the service on the tv of course, but this is just to test for now. If you check it at that location, and verify that it just stays on no matter what, the splitter or cable will be next to check. If it continues even directly connected to the wall, then it may be further up the line outside the home. Hope that makes sense. Try that now, let us know the results, and it will help us isolate where the drop is coming from! 

I haven't changed anything yet, but tonight the light isn't blinking. When I check the status page all the Power values have increased by .1, e.g. from -5.1 to -5.0. The SNRs are most within 0.2 plus or minus of the above values, a couple are a little further. Errors have only changed on one channel: channel 13 now has 17 correctable and 17 uncorrectable.

If it starts blinking again I'll perform the experiment of connecting the modem directly to the wall.

@Barmar, we appreciate you working with us to find out what's causing this. Please post an update if you see any changes.

@Barmar, If you could check your splitter next it would be appreciated and let us know if that does the trick.

@Barmar​ More head room on signal, so it's going the right way.  Did you reboot it to clear out the error counters after you bypassed the splitter or leave it powered on when you were hooking it up? 

Just a lot of errors in that post on all the channels.  You're trying to see if it runs a little better when hooked up on a cleaner line directly, or without the attenuation.  

*Edit:  If you did reboot it after hooking it up directly, and picked those errors up, then there might be something else further down the line to hunt for.  Another filter or a lightning/surge suppressor.  Something like that.  Likely where the cable enters the property. 

No, I didn't reboot. So those errors are presumably from the time when the cable was disconnected, so I didn't think they were relevant.

I just replaced the splitter. The new one  is https://www.amazon.com/gp/product/B08QVF65D8?ref=ppx_pt2_dt_b_prod_image from Amazon.com. But my power levels are no better.

@XfinityChelseaB​ I replaced the splitter today, see the above answer. But the power levels are still poor. Is the new splitter also losing 3.5db? When choosing a splitter, how can I tell? The old splitter says "-3.5db" on each of the outputs, but the new one has no such label.

@Barmar​   Spec range is from -7dB to +7dB.  (It was a larger range, but I think they're using the same DOCSIS 3.1 parts now).  You're just trying to stay within the wave and see if that can help cut down on uncorrectable errors you were seeing at higher frequencies on the end of that range, which you did.  Maybe you were drifting out of spec or performing poorly at the edges of it.  Signal power also varies a bit over time daily. 

If you get a splitter that says -3.5dB on the outputs, it's also an attenuator, so it will reduce signal, which you don't want in your case (other times you do want that depending on the situation).

If the splitter is rated for 1000Mhz like that comscope, the pass band begins to roll off before that, so you want one that is rated  to pass signal at frequencies higher than that.  1600Mhz if you are using MoCA gear or DOCSIS 3.1 at least, but you might as well use 2300MHz stuff since they make them.

To bench testing them and see what they do?  You'd need an arbitrary wave form generator and an oscilloscope to see it.  You've kind of got that though.  Your piece of test equipment that matters is your modem and the signal it sees. Reboot it and check out the error counters.  See if the blinking issue goes away.