In German the sound of 'w' in the English word "wallet" does not exist.
As a result, it is difficult for native German speakers to speak it any indeed many say "vallet" instead, which is the typical cliche German accent in English.
However, what puzzles me is an inverse phenomenon, so to speak: native speakers say the "w" sound instead of "v": e. g. "wector" instead of "vector", "conwex" instead of "convex", etc.
I'm wondering how does this phenomenon come to be? I assume the mechanism in which mistakes arise is that a native speaker "forgets" that they are in a foreign language and pronounces the words as if they were spelled in their native language. But how does this invention of new sounds / word pronunciations which don't exist in either language come to be?