I have had this problem for a long time--years.
Some multi engine planes give me a problem with advancing the throttles only results in one throttle lever advancing and the 2nd, 3rd, or 4th remains in the idle position.
I watch the tacs on start up and the engines do start up. The problem appears when advancing the throttles. Some times if I start FS over it will work properly.
I have started the engines both with the ctl/e and also with the start engine switches on the panel.
I never know how it will work. I fly the Connie a lot and notice it there more that others.
I also will happen using the 340 Saab.
Is this problem a system problem, a model problem, a calibration problem?
Anyone have some ideas to try out?