I've seen several wrong notes in Schirmer's WTC.
heavily edited schirmer for the old master is borderline complete garbage. i have seen editions where 2/3 of the page is small print editorial remarks, little of which is really of any help, let alone accurate.
on the wrong notes, yeah i've read the sentiment shared before, i believe there has even been some issues in competitions where someone learned from a schirmer and they were essentially (the competitor) told either they played wrong notes or they used music that the composer did note write.
let's talk fingerings. they're a great tool. a fantastic way to learn bad habits and possibly injur your hands.
they make great bird cage liner though. i hear they absorb animal poop quite well.
i actually don't mind their modern editions (both the 'non yellow' ones and the schirmer yellows that are 'new music', i think they share only a name and running company, there is very little editing (as the music is much newer so it is source material most of the time). the the scores are layed out quite well, i.e. good page turns, etc.
mainly stay away from 'library of musical classics' for older stuff
bad

pretty good/good

very good (and only option)-this is actually on my amazon wish list. it is freakin great. really great!

also good (non yellow stuff and modern)
ie
