As @pfm mentioned, a drying cabinet will show relative humidity, which adjusts for fluctuations in temperature. If you have major fluctuations in your bedroom (e.g., more than 10F per day), I would consider moving the drying cabinet to somewhere that is less variable.
Also, if your bathroom (shower) is in your room, that may contribute to large increases in relative humidity in a short period of time. It could jump 10-15% within ten minutes or less depending on how hot you like your shower, how large the room is, and whether there is air flow and ventilation. This would also be a good reason to move your drying cabinet.
All of this said, I have never had an issue with humidity and my cards that was actually noticeable. I think we overprotect out of fear, but the reality is that damage rarely occurs. It would have to be an awfully musty, moldy room for things to get that severe, and if you’re worried about your cards in that situation, then you need to reconsider your priorities.