The seller assured me that this was an exception, probably someone had not done after testing the cap back on the pen correctly. I pointed out to him that I have tested the pen before buying the store, where he had written properly, what hardly could be reconciled with his assumption. Nevertheless, I have let myself be persuaded to exchange the pen.
The second model was working in the store first properly, failed during use at home but then after a set. Without having the pen for inspection split, I assume that it is simply this is a bad design, a design or a manufacturing defect. My advice: Do not be fooled by the beautiful line in the store, hands off that suck.