Some brackets won't adjust snugly to both ends of the bobbin. This allows the coil to move a tiny bit on the vertical plane of the plunger. This movement robs power as the magnetic field is now moving the whole coil in addition to the plunger and everything connected to it. Even a tiny bit of slop robs power from the assembly.
Also, wallowed-out holes and posts in the link/crank assembly is just as bad or worse for robbing power.