Syncing specific custom meta fields with pll_copy_post_metas

Hey, first of all thank you for this wonderful plugin, I’ve been able to accomplish almost everything I wanted with it!

I have a problem with custom meta data sync though.

Here’s the gist of it: I’ve created a custom post type ‘events’ with Super CPT some custom meta boxes, namely ‘eventDateStart’ (which is a date – should be synced) and ‘postEventInfo’ (which is a short text for post game reports – should not be synced).

When I set the preferences to sync custom fields, everything syncs fine. I’ve tried to exclude EventDateStart from syncing with the following code:

add_filter('pll_copy_post_metas', 'copy_post_metas');
function copy_post_metas($metas) {
    return array_splice($metas, array('EventDateStart'));
}

without success. Reversely, when I turn the syncing off, and try to add a sync for EventDateStart with this code, it doesn’t work either:

add_filter('pll_copy_post_metas', 'copy_post_metas');
function copy_post_metas($metas) {
    return array_merge($metas, array('EventDateStart'));
}

I’ve also tried this with postEventInfo respectively.

Am I doing something wrong? Has this something to do with SuperCPT? What are my options?
I double checked the database and the meta_key is definitely called EventDateStart / postEventInfo.

Appreciate any help