Thank you for your time and for sharing your thoughts about my problem.
So, a tetrahedral shape of the pin indeed generates an axial thrust which pushes the pin out of its slot in the shaft. Do you think a truncated conical shape of the pin (like the one shown in my first post) could reduce this effect? Obviously then I should find an additional way to constrain the rotation between the crankshaft and the WP and then transmit the torque to the shaft of the WP