deteriorating cleanliness rating

Cleanliness has been an issue for a long time with my hostel. No matter how hard we try, it's extremely difficult to boost up the cleanliness score, which is struck in between 83% and 84% on hostelworld, based on an average of 200 to 230 reviews in a 6 month period. This phenomenon has been persistent for a year.

My staff clean every room every day for sure.
They clean public bathroom from 6:00am until 2:am , around 6 times a day.
I've added more cleaning staff.
I also believe "clean" and "new" is related, so we paint the wall and renew furniture routinely.
We wash pillows and blanket regularly too.

In fact, many complaints are pretty minor, which can usually be fixed immediately if they report to us. But many complainers just leave an extremely frustrating rating for some minor issues. A guest said his beddings were messed up by other roommates, so his rating for cleanliness is 20% (the lowest). A guest left 40% because he found a hair in a dorm.

I'm wondering how you guys keep your rating score high, especially in a shared dorm environment.

Any experience to share?