Burnt 3 years laying brick with the level bubble facing me instead of the wall, who else learned this the hard way?
Took a job in Denver where the foreman asked why my courses kept drifting 1/4 inch over 20 feet, and he flipped my level around to show me. Do you trust the bubble or the string line more when they disagree?
Ran into the same thing on a job in Tulsa back in 09, guy next to me flipped his level and watched his whole wall walk. Bubble wins every time for me because string lines sag and get bumped. Level does not lie unless you are holding it wrong.