Now just looking at this image. Do you notice how the speed line is rapidly going up and down? You can clearly see something is not right here. This part of the image you see is on the section from Sand Patch to Rockwood which is mostly downhill. As what would anybody do, I use the dynamic brake when going downhill. However, the effectiveness of the dynamic brake changes substantially. First it has almost little to no effect, then the train begins to decelerate rapidly. This kept repeating. The more dynamic brake you apply, the more the fluctuation in effectiveness of the brakes increases. As you can see on the left, I heavily oversped at the beginning of the downgrade. I had the dynamic brakes set to 8 and the train would not slow down at all. It forced me to set the automatic brake to max just to get the train down to the speed limit. My consist was 2 SD40-2's on the front of the train, and 50 autoracks behind me. My train was about 5k tons. My train should not have had too many problems going down the grade. The only thing I could think of that could be causing this is the second SD40 was doing something that was giving the dynamic brakes a hard time in the lead loco. I don't know what else could be causing this to happen. If this is not a bug, is there a way to avoid this from happening?