[shilala]

It sounds to me like your desktop humi leaks like a sieve.
If you want to prove me wrong, try this...
Put your desktop in the vino. Check it's RH prior and leave it shut while it's in the vino.
Set wet sponges (or wet paper towels on a plate, or whatever) in the vino and raise the RH of the vino as high as you can get it.
Let the whole deal sit overnight.
Next day, remove the desktop and quickly check the hygrometer inside.
If it says anything different than what it said when you started this project, it's leaky.