Bluetooth headset audio stutters only while MacBook is charging through the same USB‑C port/hub

Environment

MacBook Pro (Apple silicon) running macOS 13.5.3, using a third-party USB‑C dock connected to the left Thunderbolt/USB‑C port with a 100W USB‑C PD charger. Bluetooth headset (A2DP / Hands-Free) paired directly to the MacBook. Issue reproduces with music playback and in VoIP calls only when charging through the dock; not reproducible when on battery or when charging via a different port with original Apple charger.

Symptoms

Audio from the Bluetooth headset intermittently stutters (brief dropouts of 200–500 ms, repeated every few seconds) only when the laptop is charging through the dock via the same port. If the dock is unplugged (laptop on battery), audio is smooth. Changing the audio codec to low‑latency HFP reduces but does not eliminate disruption. Other USB devices attached to the dock are unaffected.

Observations

Console logs show intermittent Bluetooth controller retransmissions and occasional 'IOBluetooth' warnings around the time of dropouts. No kernel panics. Replacing the dock cable with a different USB‑C cable (same power rating) reduces frequency of stutters but does not eliminate them. Using the MacBook's other USB‑C port for charging eliminates the issue entirely. Firmware updates for the headset and macOS were up-to-date at time of testing.

Already attempted

Tried different cables and the dock's different ports, removed other USB devices, toggled Bluetooth off/on, re-paired the headset, reset NVRAM/PRAM equivalent steps, and rebooted. Tested with Apple charger directly into the same port (dropouts did not occur). Captured Bluetooth logs (Bluetooth debug logs) showing increased retry counts while using the dock charger on that port.

Question

Is this likely electromagnetic interference or USB‑C power negotiation causing Bluetooth instability on that port, and what safe diagnostics or mitigations can I try before engaging hardware support or replacing the dock?

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AI DIAGNOSTICS

Incident analysis

Updated 1w ago• Trouble ID

Most likely causes

EMI from the third-party charger or cable coupling into Bluetooth radio leading to packet loss 85%

Grounding or shielding problem on the dock that interferes with Bluetooth antenna performance when connected to that port 80%

Hardware-specific port routing or USB controller implementation causing reduced BT coexistence when dock is attached to that specific Thunderbolt port 55%

Summary

When Bluetooth works normally except under specific charging/hub configurations, common causes are electromagnetic interference (EMI) from the charger/cable/hub, shared antenna routing/grounding issues on the charging port, or the dock influencing the USB host controller (e.g., negotiation or leaving USB lines in a state that impacts Bluetooth coexistence). The fact that using a different charger or port resolves the issue points away from the headset or macOS alone and toward the physical charger/hub/port combination.

Suggested Fixes

Diagnostic step 1

Reproduce with minimal setup: disconnect all other devices from the dock, use a different high-quality USB‑C cable (with ferrite beads if available), and test again to see if dropouts persist.

Diagnostic step 2

Test the same dock+charger combination on another Mac (if available) to determine whether issue is dock-specific or Mac-specific.

Diagnostic step 3

Use the Mac while charging on a different port or directly to Apple charger as a workaround; if that consistently avoids the issue, avoid the problematic port/dock combination.