For a couple of sheets on the website, I noticed they are in the wrong key, I also noticed the "Fixing the sheets" project but not really any thread where suggestions for sheet fixing can be posted, maybe I just missed something though, in which case this thread can be deleted, otherwise people may want to post here, this would make the project somewhat easier right?
Anyway, the sheets I found to be a tad off key (hihi) were Route 1 from Pokemon RBY and Windfall Island from Zelda TWW, I saw something like no requests please on the project but I'd say the fixers won't need to start looking for faults by themselves, otherwise I can try fixing them up a bit myself.
Sheet fixes can really just be treated like re-arrangements for the song so most people just post corrections in their arrangement thread for feedback. You can use the Fixing the Sheets thread if you want to claim a section to work on.
Personally, I've just been picking games off the site and going through every sheet. I'll fix small errors, re-do the arrangement from scratch, or just add some articulation to the arrangement depending on how good it is. Then I just post my fixes to the submissions thread.
Right now I think only two or three people are actively fixing sheets. I'm doing Super Mario World currently, Kirby Superstar is fixing some Kirby sheets, and whenever Deku gets time, he either chips away at the Requests or Replacements.