I don't own a ACJR but I have two ACII and I think they perform as advertised.
As for your temp problem, I don't believe your symptom is a "problem", all electronic temperature sensing equipment requires calibration periodically, nothing is wrong with that if you understand how the sensors are designed and constructed. The
Neptune products I have used all have the ability to offset the sensor to correct the reading, now you just need to find a truly "calibrated" temp gage to do that with. What would be the purpose of knowing the water temp down to .1 deg accuracy? You should be watching out for
fluctuation instead. These things control heater's on and off points and the minimum differential is one degree, the best you can do is to control the tank water temperature within that 1 deg. BTW, I am not sure if the corals mind the water temp have a 1 deg swing or 3 deg swing, I know the surface water temp varies a little(maybe few deg) thru out the day in all the tropical areas I visited.
As for your clock loosing seconds, I don't know if mine does that, but why does it matter? Again I don't think the fish and coral would mind the lights are coming on or off a minuet off each day, I think nature have more daily variance.
You are right to point out the clock is off, but I don't think the accuracy of the clock is the reason you buy a controller for a fish tank. I didn't buy my last few Breitling for it's accuracy, they loose about a minuet every week:lol:. I think you should send it back for repair or maybe ask for a refund if you think these issues are important to you