Windows Shadow client performance issues?

This is pretty technical and long, sorry about that.  Hoping someone from Shadow might see this I guess.  Has anyone else observed this or can test this to verify I’m not crazy?

The Windows app for Shadow (5.0.605) appears to have some general performance issues which impacts streaming quality.  Not sure if this is known, but I’ll explain what I’m seeing.

There are 2 scenarios where a decrease in streaming performance can observed during ideal conditions… at https://www.testufo.com/, and while playing Doom Eternal (might not be specific to the game, but it’s reproducible there).

Local specs: 1Gb fiber connection, ethernet, 5ms ping to Shadow data center.  Local PC is an Alienware Area51 R2 with a GeForce 980ti.  120hz monitor.

Scenario 1: When tracking the UFOs at https://www.testufo.com/, there is a microstuttering pattern… it occurs every 8-10 seconds, like clockwork, and lasts for about 2 seconds per incident (with Shadow configured for 50mb… at lower Shadow speeds, the duration is shorter).  This doesn’t occur on my local PC’s browser. This is reproducible on a low end Windows laptop as well, with the same frequency and severity.  120hz or 60hz, no difference.

Scenario 2: Certain parts of game play in Doom Eternal exhibit much lower framerates (60fps or lower) than what is claimed by both Doom itself (FPS display) and the Shadow overlay’s “Usage stats”.  I have no doubt the 120fps data is being sent to the PC, however (at least, according to the Shadow overlay’s “Usage Stats”: the bandwidth doesn’t decrease, nor does ping or packetloss increase).

No settings in the Shadow client improve this (“Low bandwidth mode”, “Allocated bandwidth”, etc).

Is it the Shadow Windows client?

Having said that… how do I suspect it’s the Shadow Windows client and not my PC, or network? For two reasons:

1. If I connect to Shadow via Steam’s Remote Play feature, the issue does not exist.  Doom’s 120fps is definitely being delivered to the Steam client in the same area that Shadow was delivering maybe 60fps, and the https://www.testufo.com/ site no longer exhibits the rhythmic 8-10 second microstuttering.
   • Yeah, but that could still mean it’s an issue with the Shadow backend encoder! Maybe, but...
2. If I connect to Shadow with my Galaxy S9+ and watch the UFOs at https://www.testufo.com/, the microstuttering doesn’t occur at all.  So, unless mobile clients connect to a different backend encoder than the Windows app, the backend isn’t to blame.

This assumes a lot, and I have no actual knowledge about how Shadow encodes and delivers the video stream, but the results are 100% reproducible on multiple PCs.

If you read this, thanks. :)