It doesn't take a rocket scientist to figure out what's going wrong here: The puck and the puck carrier are in the corner. The Bruins wind up bunched up in that corner, but who cares? You can't score a goal from behind the goal. Instead, the Flyers follow the B's into the corner, forgetting Reilly Smith all alone on the other side of the ice.
Sigh. Clean it up, boys.