The hex wrench only fits in one position, there is a groove in the lip in the top housing and you need to turn the coupling until the hex screw head lines up. The groove is normally plugged with a dob of white silicone. The hex screw is not tightened fully tight on reassembly, the coupling needs a bit of slop. Speed control problem will likely involve replacing the control switch assembly.
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The hex wrench only fits in one position, there is a groove in the lip in the top housing and you need to turn the coupling until the hex screw head lines up. The groove is normally plugged with a dob of white silicone. The hex screw is not tightened fully tight on reassembly, the coupling needs a bit of slop. Speed control problem will likely involve replacing the control switch assembly.