I think you have a problem with overheating for the engines.
In the emd you wrote 0.021 as "te speed" factor, the current factor for 4.11, 4.10,409 buttons is 0.01.
Your engines are too hot in x min instead of x/2 min (slighly less if you divide by the right figure). AI are obliged to reduce rpm and power to recover normal T°, but as the time in the mission is going on this fact is more and more "heavy" and finaly they can not push the dead engines.
Try to reduce this factor, in HistoMod I am using 0.009, in the real life the danger is coming from too cold engine, but in normal conditions, with normal driving an engine is never too hot; remember Spit can maintain full power more than 20 min without danger in the real past!