Hello,
click on the “Functions menu” (top right corner of the MixConsole) while pressing the “Alt” key on your keyboard and select “Reset MixConsole Window”.
This bug has already been fixed, it doesn’t happen on new installations / new systems, but it will re-appear when using old preferences from an old Cubase 7 version that used to have this bug. If a project was saved with this bug, it will also reappear even if you trash your preferences. Once you have reset your mixconsole window the problem will be gone for good (at least on that project)
Regards