here is the current signal at lower resolution for a better image 

What do the modem's signal stats look like ? Try getting them here; http://192.168.100.1 or here http://10.0.0.1 

Please post the *Downstream Power Level*, the *Upstream Power Level*, and the *SNR* (Signal to Noise Ratio) numbers.

What is the exact make and model number of the modem ?

The Cable modem is an Arris SB8200

As described below

WOW ! Those first downstreams are horribly out of spec !! Something intermittent is definitely going on ! 

You can see if anything below helps / applies but you might want to have a tech out to investigate / correct this issue !

In an effort to try to obtain better connectivity, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1000 MHz, bi-directional, and no gold colored garbage from Radio Shack, Home Depot, Target, etc. Splitters should be swapped with known to be good / new ones to test.

Also check the coax cable for any damage such as cuts, nicks, kinks, sharp bends, etc.

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two-way splitter connected directly off of the drop from the street / pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.

Good luck with it !

I would agree, that is the case.

I've read all the usual information about cable health / sanity checks - and all the things I can control are good - 

as evidenced by the speed / signal strength when things are good.

How do I get a technician (onsite?) to confirm the bad signal strength so they can can escalate things / diagnose things upstream? 

Progress.

Got on a live chat with an agent

Confirmed details.

Reboot of modem made no difference.

From Agent,

O/k good luck with it ! And please post back with how things turn out.

I will let you know how things go.

Update:

Success!

Three main things have happened 

1.  I had a visit from an xfinity engineer
2.  I have learnt about the apartment cabling from the maintenance guys, and made a minor improvement
3.  xfinity Replaced (what I assume was Faulty Equipment) and all is well.

Lets break that down in detail, a post at a time

I had a visit from an xfinity engineer

After speaking to the agent, on chat, a service call was scheduled for 9-11am on Sunday Oct 17th.

Various emails / texts / notifications on the lead up to the visit telling me what I needed to do, confirm the visit etc.

The Engineer duly arrived, inspected my setup, took some measurements, and confirmed the situation.

• Yes, My Equipment (Cable modem, router) was good.
• There was signal / packet loss from upstream 
• The Signal Analyzer on the Cable modem gave an accurate picture of the incoming signal
• The Apartment complex used RG-59 cable from when it was built in the 1970's (see below)
• There should be 
  • Somewhere where the cable entered the apartment, other than where it came out in the wall(s)
  • An equipment room / closet where the cable entered the apartment building.

I was not aware of these - so we could not investigate further.

But he agreed there was an upstream issue, and would start the internal process to investigate / escalate having confirmed my situation..

Thanks for circling back with that info ! Please do so again with the future outcome. Thank you !

Apartment Cabling

The Apartment complex used RG-59 cable from when it was built in the 1970's, the Engineer said they would use RG-6 Today.

details:

https://thejonspencerbluesexplosion.com/rg6-cable-vs-rg59/

https://sewelldirect.com/blogs/learning-center/what-is-the-difference-between-rg59-and-rg6

The TL:DR; is RG59 was fine for Analog Cable TV, but RG6 is preferred for high speed internet.

However, having said that, in my case it is "good enough" - given the speeds I have been getting when everything works.

I spoke to the apartment complex maintenance guys, and yes, out building does have an equipment room, 

where the cable enters the building and is split up for the individual apartments

Identified my apartment cable (at least they are labeled), checked the connections were sound, but I'm not touching that!

It comes in via this initially ( 4 way split ?)

and then is split further by (8 ways ?)

Meanwhile I found where the cable comes in to the apartment

Its a blank unlabeled panel near the fuse box. Unless someone told you, you would not know what lies within!

A Regal RDCUV10-6 Splitter!

Set up for cable TV in the lounge , with a 6dB tap to the bedroom / office.

Guess which run I used for the cable modem?

So I disconnected the splitter, and used a coupler to directly connect the incoming signal cable (red) to the cable run  to the cable modem - as that is the only connection I use.

Hey presto 6dB more signal. 

Which moved it ( in failure mode) from "marginal" (<10 Mbps down)  to "acceptable" ( enough for a reliable connection - still not full speed - but OK) 

So that removed the "not working" frustration.

But from the spectrum analyzer - there were still two modes for the incoming signal

• "good" - flat top
• "bad" - sloping down

Which very much looks like bad upstream equipment  (amplifier) ?

xfinity Replaced (what I assume was Faulty) Equipment

With the  6dB more signal, things went well until one morning (Wednesday October 27th), things stopped working, and the signal disappeared - just like a disconnection.

So I went down to the equipment room and discovered another xfinity engineer hard at work, on a large silver box, and some much thicker cables, in a "vault" below this kind of cover

He said it would be about 20 minutes.

And then everything came back, and has worked great ever since.

All is Well

I'm now getting great speeds

https://www.speedtest.net/result/12256050309

The Incoming Signal looks great

But more importantly , given over 2 days uptime

I am now one happy camper!

@GrahameZZ 

Pretty stats !! So glad you got it straightened out !! Happy surfing !!