Is this considered to be an error on a banknote?

Hi. Upon detailed looking to some of the banknotes that i own, I noticed some ink stains around the letters on a banknotes. Actually, since they are consecutive, each one that I own from that series is over-inked at some point. I highlighted some parts, but pretty much, wherever there is a bit of text on a banknotes, some parts are either missing or some stains are added.
If someone needs high res images, Ill provide a link. Thanks.

I would not say an error. I would call it a freak printing unless you could prove that it is a constant variety. Still in that case, it's a variety not an error. I have several notes in my collection that have ink where it shouldn't be. No premium on that unless there is someone making a highly specialized collection. Some people might want a discount for buying a "spoiled" note as well.

Generally, for a note to be considered an error, with a premium value, it ought to be a note that would be removed during production because of the error, if spotted, and replaced with a replacement or star note.