Run the check
Compare the CSS-generated gradient below with an image that shows banding.
View both on another display at the same browser zoom.
Change one color-depth or display mode only if your hardware documentation supports it.
Read the result
Bands only in a compressed image point to the source; bands in both need a wider output-path check.
Limits and next step
A CSS gradient is a visual reference, not a calibrated color-depth measurement.
Repeat the check after changing one setting or connection. Keep a record of what changed before deciding whether the device needs service.