My guess is because you didn't have it plugged in, the humidity wasn't being circulated to all sections of the enclosure.
So you probably had really moist sections in there before, with some relatively dry sections.
My advice is get your RH right and keep it plugged in all the time.
I don't think I've ever unplugged mine. I used to have some fans in the bottom circulating, the air as well, but I found they didn't make a bit of difference (the box itself has a fan), so I don't run them anymore (Guess I could put them in my computer case, hmmm
)
Mine usually sits about 63 - 65 at the top (keep some beeds up high), 61-63 in the top drawer, 63 - 65 middle drawer, and 66 - 68 in bottom/bottom drawer (most of the beads are at the bottom).