The mainboard has 8 flat flex cables connected to it. 2 of them are hidden behind.

One of the flex cables may have high voltage from the flash charge circuit, so be careful when touching around. The flex cable is at the back of the unit, in the area marked with red circle in the first photo.

The bottom two flat flex cables have ZIF connectors with locking tabs. The rest are pressure fit, just pull them away gently using tweezers.