SureAI

What starsign do you have? Did you activate any mode?

my character has the Villain starsign. Sometimes I just like to explode some hearts.
---edit

no modes are active. you do mean stances right?

Yes, yes, thats what i meant. One villain stance got an archery bonus. But if you are sure theyre off, this cant be the reason either.
Try to see if it still stays there when you remove any equipment.

took off all my equipment, and turned the stance on just to be extra sure it was off, then turned it off again.
marksman is still at 104 nearly to 105. everything else seems to work fine, other than the other skills being at 104 as well.
oddly enough they don't seem to be increasing, or i'm not using them enough I suppose. well, i do have an issue with the novice gear buff, i'm not wearing any part of the outfit, but i still have the novice's embrace or whatever the buff effect is called. didn't notice that until i took everything off. as odd as that is i can't see it has anything to do with my issue, well...
i don't think of it as a problem, i just want to be sure it doesn't cause any problems, and i guess i would like to know what's going on, just out of curiosity.

I have noticed that the setboni dont update correctly, but still are correctly calculated, even if it says the wrong numbers in the effects tab.

Was the set removed by a quest at any point? OnUnequip blocks don't run when items are removed by a script, which could cause the bonus to persist.

In Oblivion the same thing could happen if you were carrying certain items when sent to jail, doing Sanguine's quest, etc.

yes, i was wearing some novice gear during such an event. one mystery solved i suppose.

as for me, my magic effectiveness is a changing number too. sometimes it's far over 100%, sometimes it's only 95%. afaik in nehrim fatigue counts in magic effectiveness however in the same gear with full fatigue my magic effectiveness is not always the same.

mine is usually around 95%, haven't looked too closely at it though.

magic effektiveness depends on Fatique and armour, but also on another factor. Im not sure what it is, but when you jump for example, magic effectiveness can increase over 100%, if you have less than 100% while standing. Like going from 95% up to 105-110%.