When you say that "it" is drawing 16mA, are you meaning the solar controller, the solar panel, or ...?
If you're measuring 16mA being drawn from the battery to the solar controller (reverse current from a charging state) that would seem concerning. However, I've not had occasion to test mine to see if it does that. I will be at that property tomorrow and I will try to remember to disconnect the solar panel and test for current from the battery to the solar controller. One big reason to buy and use a solar battery controller/tender is to eliminate the reverse flow of current from the battery to the solar panel when the panel isn't producing current. Some panels have built-in diodes for that purpose but I don't know enough to say if they "all" do.
20mA = 0.02A. Theoretically, a 5Ah battery should be able to power that load for 5 / 0.02 = 250 hours...theoretically. And that's without running the actuator/motor. But, it should get through a few long, dark nights/cloudy days okay. The real question would be the recharge rate during the day. Maybe this: 20mA draw for 24 hours = 0.48Ah drawn. 0.48Ah / 5 hours = 0.096A/hour charge rate to the battery to recover. Maybe. Throw in some losses and margin for error: 120mA from the solar charger to the battery each hour for 5 hours per day should cover that 20mA drain throughout the entire day. That may be garbage and still doesn't take into account the draw of the motor/actuator. But there should be a way to calculate how much current you need into the battery for this many hours of the day to offset 24 hours drawn at some amperage (20mA in your case).
It won't really matter so much how many volts the panel generates (as long as it's more than the minimum voltage to charge the battery and cover any system losses) as it will how much current it produces; some panels will have similar voltage output but more or less current (here, usually they're just labeled as how many Watts they (supposedly) produce). I would check the current from the panel to the solar controller while it's charging to get an idea of how much you're getting.
--HC