Don't go dropping good $ into actuators.
Most of the time, from what most owners have experienced, the problem is with binding in the ARC shock. There is a flat headed pin inside the tip of the shock. The actuator twists that pin about 30 degrees clockwise whenever you go into firm mode. Firm mode is chosen either by moving the switch from auto to firm, or whenever the ARC computer senses brake pressure, speed, or sufficient steering change.
When you hear the clickety-clickety noise from the trunk, that is the ARC computer "jiggling" the actuators back and forth a few times because one of them said that it didn't get to where it was supposed to be. [Technial term is position feedback]
The number of flashes (in auto mode) tells you which shock to look at. 1 and 2 are the rear and I don't know which is which, 3 and 4 are the front. Which it is isn't really significant because you can easily determine it. Unhook the suspected actuator from the top of the shock one at a time until you find the one which causes the flashing to stop. Leave it plugged in though. To do this for the front shocks, you pull the plastic cover off, push the 2 plastic tabs towards the center and pull up. For the rear, pull the trunk carpet back and same thing. Then turn the key on and try the switch.
When you find the problem shock, squirt a few drops of oil in the tip and twist the pin back and forth a few times with needle nose pliers. Put the actuator back on and see if the problem is fixed.
If that doesn't fix it, you may need to replace the shock or just ignore it. This doesn't rule out other problems such as the relays or even the actuator, but this is fairly common.