After 17 years back and forth, I finally solved this level. With it, I completed the medium world.
I'm so happy that I'm bouncing around my chair... ROFL
In my case, the 2 off wasn't due to a cut on the correct route. I was 2 off on a wrong route. And today, who knows why, I suddenly saw a new way to do it, that I had not seen before and that is - for me - totally counter intuitive.
At first, I was far away with it, but bit by bit, I came 2 off again and with a few more tries, I won.
So, for those stuck 2 off: it can very well be that you're on the wrong route. The correct one needs to be creative, and at start, gives the impression to create something too complicated and too long. But in fact, after optimization, it works.
Insights