Did you gather every hidden chest? There was a chest where you ignite a random isolated dead campfire and Poof! a cheat appears. Chests like those would not appear on the current Compass, so you had to stumble upon them or use a 100% accurate and complete guide; if there is such a thing.
Also, in Liyue, or is it Inazuma?… …the floating treasure boxes that have like a few hundred mora in them count towards the total for those regions, so maybe there are also some floating treasures in Mondstat?
Yea i've used complete guides that include all the hidden chests. I got inazuma and liyue at 100% already.
Like I said, i hope this helps me reach a 100% for windwail highland, but i have read stories about the area being bugged for years now so we'll see. My guess is that it's bugged.