Problem:

Car randomly losses electrical power and turns off or while it’s parked. No light, no nothing. Battery is perfect (load tested). There is power at the jump start connectors.

Fix:

There is a design flaw in the fuse-box located in the glove-box. Essentially what BMW did is make the fuse-box connection to the battery cable a simple plastic clip, instead of a bolted down connection. When the car is driven, the battery cable gets jostled and electricity arcs between the connection, and does one of two things: fries the connection, or disconnects from the box. This can be temporarily fixed by opening the glove box, removing the fuse box cover, reaching around the back of the fuse-box on the right hand side and jostling the cable until it regains the connection. This will at least make the car temporarily drive able, but it may lose its connection again.

Remarks:

Replace Fuse-box.