BME680 Strange humidity output

[tomjones]

I am testing the BME680 sensor with BSEC library. In "regular" conditions the output for humidity and temperature seems kind of reasonable, but when I put it in a sealed plastic container, this is what happens (yellow line marks the change): 

How can it be that in a sealed, small container, the humidity starts to increase? I can understand that the temperature changes since the heat has nowhere to go, but humidity? 

[BSTRobin]

Hi tomjones,

What is the environment in your sealed plastic container? Do you have standard temperature and humidity testing equipment placed for comparison testing?

[tomjones]

Hi, the container was open, with the sensor, esp8266 and powerbank inside it, prior to closing the lid. The yellow line in the chart marks the moment the lid was closed. I don't have other data for comparison, it just seems not logical to me that the humidity would rise just because the lid was closed. Gas resistance changes are understandable since the electronic components might emit some VOCs. Could it be that the humidity is calculated using the resistance value? The two charts look very much like they are inversly coorelated. 

[tomjones]

Any ideas what is going on? 

[BSTRobin]

Hi tomjones,

Cloud we know which BSEC version you used? And how many sensor have this phenomenon?
If you put out the sensor from the container, the humidity will back to normal or not?