Also, customer service. If you have an issue with a bang good purchase, you have to be willing to play their version of the customer service game. Do not expect Amazon Prime level service. The banggood customer service game involves taking a video of your issue, even if your item is completely non-responsive, send them the YouTube link, and wait a week or so. Maybe exchange 2 or 10 emails. Also, this is why I always get tracking on my banggood purchases. This way you can prove if it was a non deliver.
If you have the patience to play their customer service game, they will fix your issues. I have had probably half a dozen different issues with different orders from delivery issues, two parts missing, two Dead on Arrival speed controllers. They have always fixed the issue. A few times though, it took a while to get it fixed. 1 missing parts issue that I had involved a back order, so it took several months before I got the replacement parts. Annoying, but they eventually came through.