I have the same problem.I am an autoelectrician and recovered 2002 735i E65 today with totally discharged battery. Iwas told by the owner that whilst driving many warning lights came on....park brake fault,traction control,driver module fault,and others.
Also transmission went into limp home mode.
I assumed this was due to low battery voltage, maybe alternator not charging. fitted new battery(not AGM AS STANDARD SILVER BATTERY WAS FITTED) I haven't registered battery with power control module yet.
Checked charge rate which seemed too high 14.7- 15.1 volts.
I checked for off load discharge current and found afer 40 minutes 8 to 9 amps drain.
Like your bmw ,the seat adjust light is staying on together with the igniton switch and the gear selecter stalk.
The Park Brake yellow fault light flashed every few minutes but seems O K now after disconnecting battery again.
The navigation cd drive in boot is constantly on so I disconnected it,but still 9 amp drain and no sleep shutdown.
I will do a full system scan and clear fault codes Tomorrow .
Has any one any further ideas how to isolate modules to find the cause of the drain/no sleep.
I shall let you know how I get on.