Hello, I do not know if you still have problems, I just bought the CS757 myself. I had the Gen Drive problem initially, I think because I like to begin with engines ready to start at a gate at EGCC.
The 757 did not like this unlike another company buses/737. So I restarted with the cessna 172, started the engine, changed to the CS757 . The engines were running with everthing normal. With the APU on I turned the engines off. With the 757 at the gate I saved the flight as default. FS2004 then restarts everytime with the 757 at the chosen gate at Manchester EGCC with no Gen Drive problem.