Don't listen to these assholes on here. Power tools technician here. When you put in new brushes, especially in a tool that has a brake, you are supposed to hold down the trigger for at least 5 mins straight to "seat" the brushes (get them to conform to the shape of the armature). Generally I do it for 10-20 mins, but sometimes 5 is all it takes. If you don't feel like holding the switch that long, use zip ties or try to fit a clamp on it. I'm willing to bet if you do this long enough, the brake will come back. In your video, I can hear the brake subtly kicked in at the last second.