karelakadva

I fixed it myself, after a refreshed set of eyes! Plugin file class-es-mailer.php

Added an IF condition to also check for action = unsubscribe, since a couple of functions that prepare the unsubscribe link/text, sent that param value to the below function.

public static function prepare_link( $data = array() ) {
		/**
		 * We are getting different data like action, message_id, campaign_id, contact_id, guid, email etc in $data
		 */
		$action = ! empty( $data['action'] ) ? $data['action'] : '';

		if ( 'subscribe' === $action ) {
			$action = 'optin';
		}
		// HERE: Fixed issue of incorrect unsubscribe link
		if ( 'unsubscribe' === $action ) {
			$action = 'unsubscribe';
		}

		$link = add_query_arg( 'es', $action, site_url( '/' ) );

		$data = ig_es_encode_request_data( $data );

		$link = add_query_arg( 'hash', $data, $link );

		return $link;
	}