Surface Book 2 Performance Base dead

[astroboypaul]

I'm working on a Surface Book 2 performance base (M1032224-004 on white sticker) and would love for some help troubleshooting or where to look next.

The tablet when not connected to the base seems to work fine, but:

• When tablet is off and connected to the base, it won't turn on.
• Connecting tablet that is already on to base there is a windows device detected tone (not sure what device), but tablet remains in tablet mode, keyboard/trackpad don't work, and windows continues to report only 1 battery.
• Charger white light turns on when connected to the base, but base battery and tablet battery do not charge.
• Attaching USB-C PD charger negotiates to 20V
• Base battery was 0V but after charging at 1A CC using a power supply it is now at 11.1V
• Tablet charges ok when tablet removed from base and charger attached directly to tablet
• No visible damage and so far haven't been able to find any faulty components on the board.
• GPU has remained cold while troubleshooting
• 3P3VA = 3.2V
• +5V = 5V
• SL_PWR_EN = 0V
• No I2C signal on SDA/SCL lines (both 3.2V)

Could it be possible there is no I2C activity on SDA/SCL because U2501 (MCU) is unable to boot successfully due to corrupt firmware in U2502 (flash)? I have removed the flash and extracted contents:

Can anyone help with working flash image for U2502 please?

Am I heading in the wrong direction here? Any guidance would be greatly appreciated!