I'm currently working on a new scenario at Wath yards that begins with a diesel shunting engine coupling to two Class 76 engines and moving them to another, nearby track.
As the scenario begins, all the "spark" lights of both 76s are on, despite the fact that all pantographs are down, and my FPS rate is very low (6 ~ 8); as soon as the player engine couples to the first 76, that engine's sparks disappear and the FPS rate bumps up to 14 ~ 16; coupling to the second 76 turns off its spark lights and FPS bumps up to 20 ~ 25 or more, which is normal for me on this route. Is there a way to douse those spark lights? Neither 76 has a driver disc attached to it (when I tried adding a driver, the engines blocked the player train's path).
I'm hoping that some forum member can advise me. Here are a couple of screenshots that I also sent with my message to RSC:


{N.B.: I sent this information to support@railsim.com, who simply thanked me for my input as follows: "You comments have been kindly welcomed by our development team and will be considered in the discussions for future release of exciting Railworks 3: Train Simulator 2012 products. Unfortunately we are unable to respond directly to all the feedback or suggestions we receive from our valued customers." Valued in what sense, I wonder?}