We have not used these specific cuffs, but we have used similar "play" cuffs. Unfortunately, the quality of every set we have ever had (about 4) has been the same: bad! The locking mechanisms on these are all poorly crafted... in fact I would guess that most are made in the same factory. Sadly, even with the best handling and mildest play, these type of handcuffs seem to be prone to problems.
So, if you are looking for a pair of handcuffs that will work correctly all the time, the "play" cuffs will never meet that need. Alternatively, I recommend purchasing a pair of quality professional cuffs and slipping the "pink fuzzy" on them. When looking for a quality pair, stay away from the store brands (Lawpro or Galls) and stick to Smith & Wesson or Peerless. Even the ASP brand have had issues.