In the RAW it states that you can only train a skill once per rank.
In my games we have run into a problem. I have looked at that rule to mean that the maximum number of skill trainings are tied to your rank. So if you were rank 4 and went into a career that had 3 skill trainings open and your mandatory skill training slot available, you could gain Mastery by spending 4 advances within that career.
Our rules lawyer says otherwise. She says that you can only ever train a skill once per rank. So if you were rank 1 and you didn't train weapon skill in rank 1, and you are now rank 2, you can only train it once.
I brought up the fact that certain careers are very limited in the amount of skills available to them. Such as the Rune-Smith career. There are only 2 careers that would allow me to train Rune-Smithing, So my way of doing it would allow me to gain Mastery within those 2 careers easily. She says I would have to do 2 out of career advances to gain Mastery, and it would take me 4 ranks to do it.
My character is already Rank 4, and I want to go into Rune-Smithing, but if I have to become Rank 7 to achieve Mastery, that is crazy.