The phrase is grammatically incorrect. It is a double negative, which creates a logical error that means the opposite of what the speaker usually intends.
The correct phrase is "can hardly." While you might hear "can't hardly" in casual conversation or regional dialects, it is considered a double negative and is grammatically incorrect in standard formal writing. Gotham Writers Why "Can Hardly" is Correct is it can hardly or cant hardly free
Now you know. And you didn’t pay a cent for the answer – exactly what the word in your search promised. The phrase is grammatically incorrect