Tank ventilation system Feinleck / Grobleck detected

Hello together.

I've got another question about that mistake.
==References== ==References== 10min. Travel time it smelled strongly in the car for a short time after gasoline. Shortly after, the MKL started to operate. After that, I read out the error memory ( see Appendix ).
" 16826 - Tank ventilation system Fine leak detected P0442 - 35-00 --"
I deleted the mistake and Googled it on the net. There I read that the smell of gasoline may come from the tank. I opened both lids to the tank in the trunk once, so everything was dry. It was also dry in the engine compartment where the spritt line goes to the antlers.

The error has not occurred for the last two weeks. In that time I drove about 250km. Yesterday, after a short drive, the MKL went on again (I didn't notice a petrol smell this time) but also the windows had opened. Just read out the fault memory (see next appendix) " 16839 - Tank ventilation system Grobleck detected P0455 - 35 --

Can you tell me what else I control or control? The Commission has not yet adopted a proposal for a directive.
Thank you very much, and have a nice weekend
Greetings to D.Man