I was attempting to pickpocket the Staff Of Revenants from the guy in the Temple of Mara in Riften.

It said I had a 12% chance of success.

I put on a ring that's supposed to add +15 to pickpocket success rate.

I went to go pickpocket the staff again.

It said I had a 10% chance of success.

?

Profit

If I had to guess, I'd say there is an element of luck regarding pickpocketing. However, I'd like to get an official answer regarding the mechanics of it.

Why does the ring which is supposed to make pickpocketing easier make it harder? I expected my chances of success to go up, not down.

anyone else notice this?

I haven't put on a single pick-pocket chance increasing item or drank a potion, but that seems weird.

Are you sure it was the exact same item, same light in the area etc? If yes, plain weird and obviously not supposed to work like that.

Positive. I saved when I was crouching behind him and reloaded after each try. I guess I should take all my other items off then maybe they are gimping my character

This is clearly a bug, a serious one imo. When your chance is like 60+ to steal usually the items work fine, such is the case with lower value items. When they are 1200+(a guess, when you are max skill) value then its starts to get buggy. Here is a link that can describe better than myself http://gaming.stackexchange.com/questions/36264/is-pickpocketing-large-amounts-of-gold-in-skyrim-bugged