A couple weeks ago (I know I should have reported sooner) I was training on a skill that only had a 10% chance because I was greater than 90 points already. It took several hours, but less than 24. I think I got about a 50% success rate.
I've been training 2 skills with 18% and 30% respectively with master help, and I've been successful less often than the 10% without master help.
For the first part, you just got lucky, it happens.
For the second part, you just got unlucky, it happens.
Trust me, that the percentages are working. I just spent forever away from my master, and upon my return, I could certainly tell that I was having a better success rate.
Yes, the percentages for force training certainly do work but probability is only a probability. You can be randomly luckily if the server smiles upon you.