Maybe it has to do with the fuel delivery system? There are two high pressure fuel pumps on the V12 - which others have had problems with. How much fuel was in the tank the first time?
Also - carbon buildup is notorious - For the last 3-4 years, I've been using Chevron Techron Fuel System cleaner (available at the BMW dealership) , every 5000 - 7500 miles and that keeps my V12 running smooth.
Others may want to chime in too.