Great keyboard but key "Shift" locks (too) frequently

Superb keyboard both in design as ergonomics (curved chicklet keys having almost nothing to envy the keyboard of my Lenovo T530, three lighting adjustment levels in addition mode "off", integrated wrist rest coating specific but rather hard, hits much more enjoyable with such a flat aluminum Mac keyboard ...).
The incline settings strips could nevertheless be a little more beefy).

However, the delivered copy, the shift key "Shift" left (3 times smaller than the right) frequently left (1 out of 5 or 10) blocked in the depressed position without automatic return in high position, requiring support Additional to unlock it.
Since I often use this key, it is very unpleasant, especially since the rest of the keyboard - including the other buttons of the same size that the defective key - works perfectly and is perfectly suited me in ergonomics: j ' have referred the keyboard.

As in this case an offer reconditioned, I wonder if there were not already basically a problem with this button (replacement ...)?

Before soon order a new one, I would like to know whether other users of this keyboard have had to deal with a similar problem?