During piston manufacturing, the ends are screwed into the base. Because of this, it is possible for them to arrive with the eyes slightly misaligned.
To correct, hold the lower end of the piston stationary, and twist the upper end so that it properly aligns. If twisting requires too much strength, connect the lower end according to the assembly instructions, insert a screwdriver into the eye of the end needing adjustment and twist using the screwdriver as a handle.