Well, that's dice roll for you. And this game is based on dice roll system as far as i am aware.
So, you'll just have to deal with it.
In the first place, i don't think you're supposed to have absolutely everything in the game.
So, only natural that some of your skills which you didn't spec into will be hard to train.
Hilariously enough, no.
I even sometimes got double skillups in one day when i was past 100.
Was quite amused.
But noticed significant difficulty jump once i hit 130, i think i spent like a week trying to skillup when i hit 130 and still failed.
Hm, maybe i'll give it another shot.
I don't think skills actually have a hard cap, but things do get more hardcore the higher you go.