get_comments not working consistantly with post_id

Turns out it was my use of the language plugin (polylang)… When I call the comments it adds a language filter:

'lang' => $currentLang

So I had to explicitly override that:

get_comments(array('post_id'=>31, 'lang' => $targetLang));

I still don’t know why I was sometimes able to get the other comments without this.