The list of content types to add at user/UID/notifications/group has each content type twice:
The mistake is here, but I'm not sure what is meant to be happening with the first $content_types:
function og_notifications_add_form($form_state, $account) {
$content_types = array_filter(variable_get('og_notifications_content_types', array()));
$content_names = node_get_types('names');
foreach ($content_types as $type) {
$content_types[$type] = $content_names[$type];
}
Needs work
2.0
og_notifications
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
Correcting input format that was improperly set.
This version of Drupal is not supported anymore. If this is still an issue in the 8.x-1.x branch, please open a new up-to-date ticket. Closing.