What would cause the arch to turn early as it moves down the side of a vehicle? It happened several times yesterday and "broke" the 7-hole (horizontal) portion of the arch. As a matter of fact, this is the 2nd time in 3 weeks that this has happened, and at different locations. Instead of the shear pin breaking, the arch broke. Regarding the early turn, my site manager thought it had something to do with the sun beating down on the eyes.