Based on the pictures, it is a Montblanc 145 (Chopin/Classique) with piston converter; a counterfeit it is not according to the pictures provided. Writing failures often arise through ink deposits, especially if black ink was used previously, since it contains more suspended particles than blue ink. Helpful is, at every ink change, to flush the fountain pen with warm water and thereby keep the ink channels free. With longer writing breaks, it is recommended to fill the converter halfway with water and insert it, so that the ink line does not dry out. Platinum-plated 145s are very sought-after on the second-hand market and accordingly achieve high prices.