Point a CALIBRATED analyzer at this card — the A/V reading it shows IS this device's emission skew. Enter the negative of that reading (reading −28 → enter 28; reading +28 → enter −28): positive delays the chirp, negative advances it, so light and sound leave together.

After changing this, the analyzer's live value follows within ~3 flashes and its median within ~30 s — give it a moment before judging the reading.