Have known the steering bypass pin to fall out during pushback! Tow bar shear pins normally go.
The B744 uses the same size and shape of lockout pin as the B767 and B757. But the position of the locking pip is different. On the B757/767 it is at the end, and on the B744 it is in the middle.
So the ground crew takes a B767 pin, and pushes it in, and it stays in. During the pushback, the steering moves and it falls out. Good murphy proof design from Boeing.
The steering pin fits upwards into the mech, and so falls out when it fails.