Effect of Internet Service Quality on Streaming?

Based on your comments above, and the fact that your SQ is great sometimes and poor other times, as I stated above, I suggest you ask your Internet service provider for an in house audit of your Internet signal coming into your home. In addition, please check your router to ensure its software is up to date and working okay.

Your Internet Service Provider needs to check the signal both outside your home and inside In other words, is the signal strong and solid outside your home at the junction box and still strong inside your home at the point of entry and at the cable modem. Please confirm the cable modem is their current model.

For example, my Internet signal was very poor at the outside junction box because of poor wire connections He replaced all connections at the junction box and all connections at the box on the side of my home. Unfortunately, these connections go bad after time and impact the signal. This is why I am suggesting your ISP audit your signal, connections, etc. He also replaced the cables and connections inside my home. Everything worked perfectly after these corrections were made.

@nyev

I would try Muon Pro filter between your Innuous switch and Streamer. Comes with 30days money back guarantee.

@lalitk , I have a Muon Pro, two Network Acoustics ethernet cables, and a Tempus switch on order, to replace my Innuos PhoenixNET and two Audioquest Diamond network cables - assuming I don't return it all in 30 days that is....

That said I still don't know at this point if my issues are due to network degradation (which I DO see on measurements during periods of bad quality), or AC power noise, or both.

I've downloaded from HDTracks a 16/44 version of a test track I use a lot and put it on my server.  Right now, both the Tidal streamed version and the local file sound fantastic.  Different, but both great.  A bit better image specificity on the local file but really I enjoy them both.  I will wait until I get crap quality again, and do another comparison.  If they are both bad, I suppose it means AC power noise is the limiting factor.  If the local file is much better, then I will 1) see if the Network Acoustics gear changes things when it arrives, and 2) follow up with my ISP as @hgeifman suggested.

@nyev my system is plugged into two dedicated circuits. The sound is better after 11pm. Everything is quieter, my family members including my dog are not running around. Sound is fantastic. I tried Ethernet filters (N A Eno streaming system) and it changes the sound yes, but does it filter anything? May be. But it didn’t mitigate the lower performance of my system until that quiet moment after 11pm comes. 
So in my opinion it’s a mix of everything that uses electricity in your house plus people who quit disrupting our listening before midnight. Doubt it’s Ethernet/internet quality.