diff --git a/phpBB/language/en/email/mention.txt b/phpBB/language/en/email/mention.txt
index 51c161453e..95bc4c8601 100644
--- a/phpBB/language/en/email/mention.txt
+++ b/phpBB/language/en/email/mention.txt
@@ -1,20 +1,20 @@
-Subject: Topic reply notification - "{TOPIC_TITLE}"
+Subject: Topic reply notification - "{{ TOPIC_TITLE }}"
 
-Hello {USERNAME},
+Hello {{ USERNAME }},
 
-You are receiving this notification because "{AUTHOR_NAME}" mentioned you in the topic "{TOPIC_TITLE}" at "{SITENAME}". You can use the following link to view the reply made.
+You are receiving this notification because "{{ AUTHOR_NAME }}" mentioned you in the topic "{{ TOPIC_TITLE }}" at "{{ SITENAME }}". You can use the following link to view the reply made.
 
 If you want to view the post where you have been mentioned, click the following link:
-{U_VIEW_POST}
+{{ U_VIEW_POST }}
 
 If you want to view the topic, click the following link:
-{U_TOPIC}
+{{ U_TOPIC }}
 
 If you want to view the forum, click the following link:
-{U_FORUM}
+{{ U_FORUM }}
 
 If you no longer wish to receive updates about replies mentioning you, please update your notification settings here:
 
-{U_NOTIFICATION_SETTINGS}
+{{ U_NOTIFICATION_SETTINGS }}
 
-{EMAIL_SIG}
+{{ EMAIL_SIG }}
diff --git a/phpBB/phpbb/mention/controller/mention.php b/phpBB/phpbb/mention/controller/mention.php
index 0aa08e090b..6548a8a995 100644
--- a/phpBB/phpbb/mention/controller/mention.php
+++ b/phpBB/phpbb/mention/controller/mention.php
@@ -14,6 +14,7 @@
 namespace phpbb\mention\controller;
 
 use Symfony\Component\HttpFoundation\JsonResponse;
+use Symfony\Component\HttpFoundation\RedirectResponse;
 
 class mention
 {
@@ -45,7 +46,7 @@ class mention
 	{
 //		if (!$this->request->is_ajax())
 //		{
-//			redirect(append_sid($this->phpbb_root_path . 'index.' . $this->php_ext));
+//			new RedirectResponse(append_sid($this->phpbb_root_path . 'index.' . $this->php_ext));
 //		}
 
 		$keyword = $this->request->variable('keyword', '', true);
diff --git a/phpBB/phpbb/mention/source/base_group.php b/phpBB/phpbb/mention/source/base_group.php
index 9a8c70695c..b8d6c44091 100644
--- a/phpBB/phpbb/mention/source/base_group.php
+++ b/phpBB/phpbb/mention/source/base_group.php
@@ -33,6 +33,9 @@ abstract class base_group implements source_interface
 	/** @var string */
 	protected $php_ext;
 
+	/** @var array Fetched groups' data */
+	protected $groups = null;
+
 	/**
 	 * Constructor
 	 */
@@ -58,9 +61,7 @@ abstract class base_group implements source_interface
 	 */
 	protected function get_groups()
 	{
-		static $groups = null;
-
-		if (is_null($groups))
+		if (is_null($this->groups))
 		{
 			$query = $this->db->sql_build_query('SELECT', [
 				'SELECT' => 'g.*, ug.user_id as ug_user_id',
@@ -76,7 +77,7 @@ abstract class base_group implements source_interface
 			]);
 			$result = $this->db->sql_query($query);
 
-			$groups = [];
+			$this->groups = [];
 			while ($row = $this->db->sql_fetchrow($result))
 			{
 				if ($row['group_type'] == GROUP_SPECIAL && !in_array($row['group_name'], ['ADMINISTRATORS', 'GLOBAL_MODERATORS']) || $row['group_type'] == GROUP_HIDDEN && !$this->auth->acl_gets('a_group', 'a_groupadd', 'a_groupdel') && $row['ug_user_id'] != $this->user->data['user_id'])
@@ -86,14 +87,14 @@ abstract class base_group implements source_interface
 				}
 
 				$group_name = $this->helper->get_name($row['group_name']);
-				$groups['names'][$row['group_id']] = $group_name;
-				$groups[$row['group_id']] = $row;
-				$groups[$row['group_id']]['group_name'] = $group_name;
+				$this->groups['names'][$row['group_id']] = $group_name;
+				$this->groups[$row['group_id']] = $row;
+				$this->groups[$row['group_id']]['group_name'] = $group_name;
 			}
 
 			$this->db->sql_freeresult($result);
 		}
-		return $groups;
+		return $this->groups;
 	}
 
 	/**