Mine
does not have a big steel knob like that on top. You said remove it. did you add it? I would think the big heavy weight would help keep the pintle seated.
The new furnaces all come with a big steel knob for lifting the valve instead of the wooden ones. Repurpose it to the pintle and put a wood one on the stud you took it from so you don't get burned working the valve.Remove the steel knob, redrill and tap it to the pintle threads