I'm a little curious how that screw got in there in the first place. That's a flat head countersunk screw, which seems to be only used for the front and back panels. The ones under the front panel can't go anywhere because they are covered, and the ones on the back are too big to fit through the vent. It looks like someone just dropped one in there and was too lazy to bother removing it. Which only adds to the questionable quality control. For the price, you can't really complain. Plus the majority of the people here on the forum have the skills, equipment, and desire to fix stuff like this. I can't guess what the percentage is of getting a unit with issues, but for total beginners buying their first station, or people that aren't on this forum, it's probably a good idea to post some of these concerns/issues in the feedback on AliExpress. Plus it might get Aixun to address these random problems.