Language file keeps reverting

Hi

I’ve installed WP 4.3.1 & the latest woocommerce. For some weird reason my .po and .mo files keep reverting. There are some words in my translation that I would like to adjust to better fit my content.

When I upload my files, all is well, but after xxx amount of time, somehow the original language files seem to reappear.

I’ve figured out i have to use this code.

add_filter( 'auto_update_translation', '__return_false' );

but i don’t know where to put it, in the documentation it sais not to put it in the config.php

any help would be more then welcome, i’m desperate 🙂