Blacksmithing Fine Plate and Beyond

[KENAK]

I've been having zero luck with my combines as of late, where I almost never have a skill up despite having 170 STR (or even 200+ when I have my buffs on).

It seems that for about every 20 combines I get one skill up, though earlier today I did 5 combines for Ornate Chainmail and 20 for Fine Plate Visors, where I did not get a single skill up.

Do skill increases become extremely rare in the ~180-190+ skill range, is my strength too low, or am I just extremely unlucky? Because it is incredibly frustrating to spend hours gathering materials to not have a single skill up. Not to mention the drain on my platinum. If I am not doing something wrong, I'll probably abandon this as it's not worth the hours upon hours of my time to see that little skill number increase by 1.

For reference, I have a blacksmithing skill of 191, and neither ornate chain mail nor fine plate visors tell me I can no longer increase my skill making them.