Word/term for persistence in incorrect pronunciation

Mumpsimus

I think this is described almost perfectly by the word mumpsimus:

1. adherence to or persistence in an erroneous use of language, memorization, practice, belief, etc., out of habit or obstinacy (opposed to sumpsimus).
2. a person who persists in a mistaken expression or practice (opposed to sumpsimus).

Origin of mumpsimus

1520-30; from a story, which perhaps originated with Erasmus, of an illiterate priest who said mumpsimus rather than sumpsimus (1st plural perfect indicative of Latin sumere to pick up; see consume) while reciting the liturgy, and refused to change the word when corrected

(Dictionary.com Unabridged; Based on the Random House Dictionary, © Random House, Inc. 2017.)