by setting your voltage references in physical proximity to each-other, with a divider between the photo-resistors, you can use the casting of shadows, and movement of the sun to let your circuit auto-calibrate.
The arduino gives an error and resets after the actuator moved for a couple of seconds.
Have you really wired it up as shown on the Fritzing diagram? If so, then you've got a short across the 24V supply, via the Arduino, because both sides of the 24V supply are connected to Arduino ground (one via each Arduino ground pin).
Since errors come from code and not the Arduino, what is your code?