MacBook Pro 14″ (M4, 2024) boots on battery but shuts down on charger

Model & history

MacBook Pro 14″, late 2024 (M4, base model)

• Tea spill on keyboard ~4 months ago. Local shop did a cleaning - no parts replaced. Machine has worked perfectly since.
• Battery still healthy; macOS Sequoia.

Current symptoms:

1. If I power up on battery alone, the Mac runs normally (until it dies from low battery).
2. As it's low battery, when I power up I get a message that displays the "runs on reserve battery life" and the macOS first shows the yellow-triangle “The version of macOS on the selected disk needs to be re-installed” screen. When I click Recovery → Reboot the macOS from Recovery, the Mac runs normally .
3. The moment I attach any external power—Apple 140 W brick + MagSafe 3, or known-good 96 W brick over USB-C, or USB-C on the opposite side—the MagSafe LED blinks amber for ≈1 s and the whole laptop shuts off. Same behaviour on both USB-C ports.
4. Reconnecting the charger while the Mac is off causes a brief blink, then nothing. Unplugging the charger lets me boot again on remaining battery.
5. Tried three different chargers and two MagSafe 3 cables; cleaned all ports with 99 % IPA; let it dry 24 h—no change.

What I’ve ruled out / measured:

• Charger and cable (swapped).
• MagSafe DC-in board (visual inspection—looks clean, no charred pins).
• Battery fuse appears intact (machine boots on battery).
• Liquid-detection lock doesn’t match the hard power-off I’m seeing.

Suspicions from research:

• Faulty RAA489900/RAA489901 charger IC (U7200) or shorted PPBUS bulk cap.
• Less likely but possible: both CD3219/3220 USB-C PD controllers or the ideal-diode MOSFET pair.
• Repeated hard shut-offs are probably what corrupted the Signed System Volume and trigger the yellow-triangle screen.

Goal:

Figure out the issue and whether a U7200 re-chip (or cap swap) is worth attempting if that's the cause.

Thanks in advance for any schematics, voltage points, or hard-earned wisdom you can share!