I have 3 Mikrotik Routerboard 750 R2.
Before update firmware of them, It has 128M Disk space and 80% Free, But After upgrade two of them, It changed to 16M and 18% Free, Why ?!!
Please See the attached photo.
Please see the attachments,RB750 R2 is supposed to have 16MB flash.
Can you please post what you get in System -> Resources on both routers (the one affected, and the one that is not).