wp_insert_post called via cron duplicates posts instead of updating them - wordpress

Question

I'm currently stuck on a problem I can't figure out on a wordpress side project. Here's the thing :
I made a plugin that queries an API, and processes its data to insert posts.
The problem I face is that, when the main function is triggered manually (i.e. via a route or cron manually launched) posts are correctly created or updated, but when the cron executed automatically, posts are always duplicated. I may have narrowed the problem down to capabilities (I check if posts exists by querying the cpt for a unique meta-field), and when the cron executes on its own, it find no ids.
Here are code samples :
public function insertPosts() {
set_current_user(1); // <- here I tried setting the user as admin for the script, but it didn't work
// First, get all prestations from the api
$prestations = $this->api->getPrestations();
/*
* Then :
* we remove sessions of formations initiales, which are useless (gamme id 10 = formations initiales)
* I could have "only" taken the ids I need, but unsetting useless array entries allows for a lighter dataset
*/
$prestations_info = [];
foreach ($prestations as $key => $prestation) {
if ($prestation['gamme']['id'] == 10) {
// Removes the useless $prestation and breaks out of the loop so its ID's not stored
unset($prestations[$key]);
continue;
}
$prestations_info[] = [
'fid' => $prestation['id'],
'cat_name' => $prestation['gamme']['name'],
'cat_id' => $prestation['gamme']['id']
];
}
/*
* Then :
* Parse the array to process every id individually and query the api for core informations for the singles
*/
foreach ($prestations_info as $presta) {
// Meta query to check if a post with the formation's id already exists
$args = [
'post_type' => 'formations',
'posts_per_page' => -1,
'meta_query' => [
[
'key' => 'api_fid',
'value' => $presta['fid'],
'compare' => '='
]
]
];
$posts = new WP_Query($args);
if ($posts->have_posts()) {
while ($posts->have_posts()) {
// If a post with that formation id already exists, we retrieve its ID:
// this way, we can update existing post and avoid duplicates
$posts->the_post();
$post_id = get_the_ID();
}
}
$body = $this->api->getSessionsByPrestationsId($presta['fid']);
$post_array = [];
$locations = [];
$nb_places = [];
foreach ($body as $key => $item) {
if (!empty($item['seances'])) {
$duration = BOUtilities::getFormationDuration($item['seances']);
$dates = BOUtilities::getDatesPerSessions($item['seances']);
}
if ($dates) {
$session_date = [];
if (is_array($dates)) {
foreach ($dates as $i => $date) {
$session_date[$i] = [
'dates' => $date['start'] .' - ' . $date['end'],
];
}
} else {
$session_date[] = [
'dates' => $dates,
];
}
}
if (!empty($item['location'])) {
$locations[] = strtolower($item['location']);
$session[] = [
'sessions_location' => $item['location'],
'sessions_dates' => $session_date,
];
}
if (!empty($item['nbplace']) && $item['nbplace'] != 0) {
if (!in_array($item['nbplace'], $nb_places)) {
$nb_places[] = $item['nbplace'];
}
}
if ($item['price'] != 0) {
$prices[] = $item['price'];
}
}
$formatted_cost = BOUtilities::setPrices($prices);
$effectifs = BOUtilities::setEffectifs($nb_places);
if ($post_id) {
$post_array = [
'ID' => $post_id,
'post_type' => 'formations',
'post_title' => $item['prestation']['name'],
'meta_input' => [
'api_fid' => $presta['fid'],
'aside_cost' => $formatted_cost,
'aside_duration' => ($duration > 1 ? $duration . ' jours' : $duration . ' jour'),
'aside_effectifs' => $effectifs,
]
];
$inserted_post = wp_update_post($post_array);
}
else {
$post_array = [
'post_type' => 'formations',
'post_title' => $item['prestation']['name'],
'meta_input' => [
'api_fid' => $presta['fid'],
'aside_cost' => $formatted_cost,
'aside_duration' => ($duration > 1 ? $duration . ' jours' : $duration . ' jour'),
'aside_effectifs' => $effectifs,
]
];
$inserted_post = wp_insert_post($post_array);
}
// The cron does not have the capability of adding taxonomy terms, they need to be be added separately
$inserted_terms = wp_set_object_terms($inserted_post, $presta['cat_name'], 'categories_formations');
$inserted_terms = wp_set_object_terms($inserted_post, $locations, 'ville');
update_field('aside_sessions', $session, $inserted_post);
unset($dates);
unset($session);
unset($formatted_cost);
unset($nb_places);
unset($prices);
}
}
This is very much work in progress, but, for now, I am stumped.