That's a bit strange. My old 14mm would focus past infinity, hence the fix in the video which I did, but my previous Samyang 35mm would pretty much stop right at infinity. Is it possible that something is inside which is preventing it from focusing? I don't think it would take much but I'm not sure how to disassemble the lens to check.
I opened it and had a look, and I'm afraid you're right..something inside the body of the lens is actually stopping the lens from hitting infinity/falling short from infinity. Such a shame, and the company it was bought from isn't helping either.
I guess it will just stay as a close up lens..