The error in the newspaper article is accidental.

Solution (By Examveda Team)

Accidental : happening by chance, unintentionally, or unexpectedly.
Permissible : permitted; allowed.
Usual : habitually or typically occurring or done; customary.
Conventional : based on or in accordance with what is generally done or believed.
Intentional : done on purpose; deliberate.

Antonym of Accidental is Intentional