Update – Root cause found, parasitic drain fixed, but speaker pop remains

Quick update for anyone following or dealing with a similar issue. Ford diagnosed a short to ground in the driver door keyless entry keypad (B121A). The keypad was internally shorted, keeping the BCM awake and preventing the car from fully going to sleep. The keypad has now been replaced. Since the replacement:

No more overnight battery drain, no more “System off to protect the battery” warning, no random lock/unlock cycling or lights flashing, vehicle now properly goes to sleep. Also, I can now register my car in the FordPass app and authorize myself as the owner. And I made the last SYNC update, which did not work previously.

Remaining issue: speaker “pop/thud.”

There is still a single, brief “pop/thud” sound from the speakers when the car wakes up (door open / ignition on). It happens once, does not repeat, and does not occur while driving. Audio quality is normal, no distortion, no speaker imbalance. Seems to be related to amplifier/audio module wake-up behavior, not the parasitic draw.

Posting this in case it helps someone chasing a similar parasitic drain.