On Zoom if the cellular bars icon goes yellow or red, it indicates an issue with the connection. Zoom's FAQ is rather bland in how they describe it, but essentially when you have a poor connection, those yellow/red bars indicate there is a connection issue between you and a specific user. However, they don't elaborate.
Zoom for what it's worth is a CPU Hog. So if a system has allot of other tasks, Zoom quality can be an issue. Now, in some cases it's understandable, as when I run it on a Intel Atom X5, it's just barely enough power. Add to that Windows doing a "feature update" despite the machine being in use and within the daily active hours...it tanked.
So something similar might be happening. In most cases Zoom will show a message saying the CPU is causing quality issues. But they might have missed it or it might be below a threshold but still able to cause disruption.
Zoom is also poor at managing network speed. If bandwidth is low, it's supposed to go in low resolution mode and shrink the window and show a message under the person that has poor bandwidth. However again, often it doesn't and instead may stutter etc.
Most consumer upload speeds at home are rather paltry. The ISP always emphasize download speed but for Zoom it's critical to have a fairly good uplink too. If they are wireless it only adds to the bandwidth issue.
Some things you can go through are verify internet speeds, check Windows update history (it may have kicked off in background hogging CPU cycles), make sure the system gets a reboot at least once a week. (Not shut down, REBOOT. Damn Fast Startup)
