how many thermometers are you using? have you verified that your thermometer is correct? I've seen 5 degree differences in thermometers and rarely one just outright goes hay wire, especially if it's ever been over heated. I'm still a nube but I've read just about everything I can get my hands on about BP's here and other places and it seems like the consensus is that 75 f is the lowest things should go anywhere in the enclosure. thanks to the suggestions here, I got a temp gun and it has put a lot of fretting to rest since you can get the actual surface temp of the body of the snake and surface area of hides, floor etc. if you don't have one, it's money well spent! I shoot for upper to mid 70's in the coolest spot in the tank. ours are active at night now that I have things dialed in and I think that's normal if they are comfortable. "calming down" by going into a hide at night may be a sign it is cold, not happy. but if your thermometer is reading low when it's actually more like 75-78, that could explain it to. I have not noticed any clicking yet, it may be a respiratory anomaly or it could be a sign of low grade fluid in the lungs, which seems possible without infection (like walking pneumonia sometimes is). does raising the temps make the clicking go away?