It IS up to you, though. It’s part of the process. You check all screws and rings to make sure everything is tight.
The quality control on Chinese flashlights can be iffy, plus the long distance travel can cause things to loosen up. I do it on every light I purchase. You learn this from experience and it’s passed down to others so they can learn before a bad thing happens to them.
No worries, though. It’s not your fault. The driver problem may not even be related to that brass cap.
Here is a picture that Lexel posted on his mf01 preproduction review.
I never realized what that little piece was in his picture. Now it makes perfect sense. The pcb’s on the end make the center rod and the brass caps all positive. The outer rings and 4 outer posts are negative. Hence why they are covered in insulating heat shrink.