[D. Generate]

I may be pointing out the obvious but have you calibrated your hygrometers? I've had some read way off what actual conditions are.

What temperature are you running? In itself it might not explain fluctuations but does influence humidity so opening and closing might cycle the unit and therefore affect your numbers.

Apologies if repeating what you know. I have two 28 bottle coolerdors going for the last two weeks and I still haven't quite hit the sweet spot.