Mistake: Buying based only on the 'solved' product photo.
Correction: This is the #1 mistake. The beauty of the finished ring tells you nothing about the mechanism. Always look for a photo of the ring disassembled into its six separate bands. This shows you the shapes, the interlocking points, and the sheer number of pieces you're committing to manage. It transforms the purchase from a jewelry buy to a puzzle buy, which is exactly what you want.
