What altitude are you trying to fly with the Matrice? We will have to try it out here. They may have changed limits or something but we didn't see any of that during out testing.
There is one extra thing that will slow a mission down now. Previously you could select a max speed that is lower than the one that gets calculated or the height of the aircraft and overlap settings would determine the Max Speed value that gets populated in the Flight Plan stats panel (top left).
Now, on the way to the start of the flight plan the exposure value is monitored along the way and is used to calculate an average exposure time that is likely be used for the mission. This value is used to calculate a maximum speed the aircraft will be able to fly to keep the ground smear to less than 2 GSD units. There is a popup message to tell you that this is happening.
If you are flying in low light, the aircraft will slow down based on the light available. We had far too many people flying too fast for the conditions and getting blurred imagery. This is a way to make sure the imagery being collected is useful.