when you say stopping semi, are you meaning you're getting lockups?
active brake will try to stop the motor the moment the cutoff lever trips, depending on how fast the build is and how strong the motor is it's possible for it to stop so quickly that the cutoff lever is still disengaged which will lock the trigger, forcing you to switch to auto to get it moving again.
depending on the setup this might happen very rarely, or so frequently it locks up basically every shot.
this is one of the reasons i tend not to suggest mosfets with just active brake (active brake is necessary for fancier setups using precocking).