I would suggest a few things the first thing is your hygrometer accurate? A salt test will confirm this although it is hard on digital units. Digital units are hard to calibrate but a purchased kit from a smoke shop can be used to do so. Digital units have either very good accuracy and are ridiculously expensive and very fragile. Or they are cheap and questionable accuracy and become more so as cables are pinched and probes dirty.

I would question if you have enough ventilation if you are seeing spikes like that. If on paper towels you remove the snake and water bowl how long will it take to reach the room RH? I personally am unhappy with anything less than one hour. (this is roughly one air change per hour) I would be concerned that too little generate an abundance of bacterial and such in the enclosure. The creates the snake version of 'sick building syndrome' where a building is too tight.