Unusable ever tested before series production?

The knife looks quality and feels good in the hand but it was already. One has to be able to use the actual power button permanently hold the safety switch. This requires a lot of power such that it is on the one hand and on the other hand leads tiring that the slightest slackening of spasmodic "button is held down" the blade stops. An absolutely useless knife in which the question was raised whether it was ever tested in practice by test subjects before mass production.