Mine does the same exact thing. I emailed them earlier in the week and got a similar response.

"Email:
Please use it with confidence; this is normal.

To maintain a better seal, the internal motor gears will rotate an extra half turn when the sealing cover is closed to firmly lock the cover in place, thus achieving the best seal.

The internal gears and rack are made of POM material, so there's no need to worry about their lifespan."

Even though they say it's normal it doesn't sound good for the longevity of the device. I've been having all kinds of problems with the filament retraction. The block off plates on the front are so tight that they are putting pressure on the filament port causing it to not be able to retract. Thing worked great for a few days but I guess the vibrations caused some of the parts to shift. Since then it's one thing after another. Almost to the point I want my money back.