I can't figure it out either. My Combat Training is maxed, but even if I mash the keys, I can't win. The problem honestly seems to be when you have to swap from right to left. I ALMOST had the fisherman, but the moment the swap happened, even though I quickly jumped over, I went from almost the end of the green area to right near the beginning of the red. I have Cubital Tunnel Syndrome (writer's/reader's elbow), so I'm thinking that fucks me a little in the switch because I can't mash with my left pink or index finger, but even swapping so my right hand is free for the transition sees the same thing happen. It's almost like he gets a bonus on that swap. The only thing I can think is I may accidentally hit the wrong key one time because my index finger will start to slightly spasm if I mash for too long. It's ridiculous. It's been about a year since I played, so I expected some mechanics to change and create a learning curve, but this is driving me mad.
I can't figure out if this part of the game is inaccessible to me because of my SLIGHT disability, if the mechanics are screwed up, or if I'm simply doing something wrong.
Edit: I just beat the fisherman and blacksmith. I had to save-scum a few times, but I found that more rhythmic tapping worked better then trying to go all out. It still took forever, but it is doable. I think it comes down partially to how you approach the mashing and partially luck (if it starts with right taps, I'm usually screwed because I can transition from left to right more quickly. I basically had to swap out hands once my right hand had a decent rhythm going to free up the hand for the next transition. If I got caught having to transition with my left hand AT ALL, I would lose no matter how far ahead I was originally. I think there's a bit of a balancing issue going on (perhaps they forgot to change to the new skills-style system of the arm wrestling mini-game, meaning it's still expecting MUCH higher digits than the new system allows), but I think it may also be a slight accessibility issue.