If you search WordPress core for
> you will find the function
Then if you search for
_wp_specialchars you will see it is used in
esc_js (as well as
esc_attr) so do not use
esc_js, escaping is mostly for output anyway.
Further search results show that in
_wp_specialchars is added to multiple filters with a priority of 30. So what you would need to do is find out which filter is being applied to your text area value before saving, so that then you can do this before saving:
remove_filter('NAME_OF_FILTER_HOOK', '_wp_specialchars', 30);
It is hard to be more specific than that without the actual code used, but this should give you enough clues to find what you need.