Yeah, the Delta RSDs click as the sun comes up in the morning, I can't hear the ones in my attic unless I'm in the attic when they do it, but there are two in the garage that I can hear from my dining room table. The RSDs are just relays controlled by a signal coming from the inverter. I'm pretty sure what happens is in the morning once there's enough voltage from the PV to activate the relay it clicks on, but then the loading presented by the inverter now being connected causes them to trip off again, until there's enough voltage coming from the PV that they can stay on. My RSDs do this for maybe a minute or so each morning. I don't think this is a problem, it's just what they do when they're right on the border of their minimum operating voltage. Some of my RSDs were replaced for a different issue, and the new ones click just like the original ones did.