Just wanted to clarify a few thing, You do not have to do this work from the roof.
When I was referring to the four screws on the outer cover, should have called it the interior trim ring. Almost everything on the Northern Breeze can be access from inside once the trim ring and fan blade cover is removed.
Have been wanting to clean the screen on my living room fan, so this morning I remove it for cleaning. It was easier for me to remove the trim ring and then the fan cover, both needed cleaning.
If you have the Northern, on MY unit which is older, the motor to raise the lid is self contained. It is a sealed unit with no exterior parts to replace. It is attached with three screws. The lid arm has the same two screw mounting as the manual units. The connection between the arm and motor is a six sided shaft plug in arrangement.
I would check that all the mounting is tight. Would ensure that the vent lid is fully closed and no windows open when traveling. I can raise my lid manually by pushing up on the knob while turning, it feels spring loaded, but might check it also. If you need parts, believe Ventline will sell direct.
Let us know what happens.
Chris