Perks Fail To Progress And Reset After Every Game

We are aware of the problem and working on it. For now you can delete the KillingFloor/System and Cache files located on your system. On a Mac they should be located in these locations:

Username/library/applicationsupport/killingfloor/
and
Steam Content>Common>Killingfloor>

On Linux the files are located in the following location:

home directory ~/.killingfloor/

At that point avoid using mutators and it should not happen again.