Maybe you wanna try this.
1. Remove local Time Machine backup. Source
here, look for answer from username HevvyD
a. Open terminal
b. Type "df -h". This will show you a volume of MobileBackups if it was enabled and if this does apply to your system.
c. To disable your Mobile Backup, type "sudo tmutil disablelocal". When prompted for password then type in your password.
d. Check your Storage and see that the purgeable space has been deleted plus the System section has also shrunk to just contain the OSX.
2. Using tricky partition. Source
here
3. Disable Optimized Storage feature.
I've already using no.3 but no luck.