Run the check
Repeat the same key press in a plain text field and the affected app.
Run the browser latency tool in a foreground tab with no background load.
Compare wired and wireless connection or disable one processing effect.
Read the result
Lag limited to one app suggests its own input or rendering path.
Limits and next step
Browser timestamps cannot isolate switch actuation or display photon timing.
Repeat the check after changing one setting or connection. Keep a record of what changed before deciding whether the device needs service.