I´m pretty sure the issue lies in your “I charge the Evis-special to do the job.”
There are 2 ways that can fail there.
a) You stuck in the mutant, so the game says “you don´t charge anymore”.
b) The special from Evis does multiple hits, but the game wants the mutant to be dead on the first hit after charging.
So… just pick an axe, charge in with a heavy and call it a day i guess. (Or just don´t use your special on the Evis.)
You have to kill it while dashing.
Not right after dashing.
So like Darth said, you have to insta bonk the mutant.
Go to the meatgrinder and you will see that you can start your attack animation while dashing, and finish the attack before the dash ends.
It needs the right timing but is definitely doable.