Can't change encoding of just one page/plugin

Hi, One of my plugin’s translation file uses a non utf-8 standard for its encoding. The plugin’s content (it’s a contact form) is featured on one of my pages.

I tried to set this individual page’s encoding to the languages old encoding system in Options > Read > [Selecting the page from the page list dropdown menu], but the change affects the entire site messing up the encoding for all the other characters in the navigation and in all other pages and posts.

I currently fix the encoding in the translation file and then re-upload it, but every time there is an update for the plugin I have to do it again.

Any advice?