This "might be" due to the fuel inlet hose in the tank being cracked or perforated at a point above the in-tank fuel screen.
What would be happening there is that when the blower is oriented in the normal position, the defective section of hose is out of the fuel and sucking some air.
Tilting the blower at an angle possibly causes the split to submerge and suck only fuel.
That would be where I would check first.