Nevermind, I just did some quick surgery on the samyang and now it focuses correctly to infinity as it is supposed to be without the stopper getting in the middle . The procedure is similar to the one for their 85mm and other manual prime lenses. Not the first lens I have to do this to but definitely one of the easiest ones https://www.dyxum.co...topic76615.html
1) Peel the rubber out
2) remove the 3 screws at 120 degrees. That will allow to retreat the focuser ring and access the stopper silver colored plate with its two screws. Move a bit the screws so that the stopper allows to move past infinite (the adjustement is just of a couple of mm, not more).
3) fix again the 2 adjusting screws to fix the stopper to its new position.
4) move the focuser tube back to its place and check (in my case I did it with a star) the focusing point to infinite so that we can put the focuser with its scale back to its correct position.
5) screw back in the 3 120 degrees screws.
6) Put the rubber band back in
Enjoy the lens .