I agree with cls515 - get the beads for a more permanent solution.

It's been pretty dry in the Hill Country - right now the rh in Austin is 50. A small humi is going to fluctuate - humidity leaving when you open it and then building back up when you compensate (and maybe over-correct?). It could be that the box came from a climate where the rh is more cigar- friendly and rh maintenance wasn't an issue.

At any rate, a more permanent solution here is a larger box with a very good seal, filled over 1/2-way with cigars, or, a cooler - 48 quart or larger, where humidity leakage will be much less.

And, analog hygros are often unreliable. Get a digital one.