diff --git a/game_manager_frame.php b/game_manager_frame.php
index 3381425..e5dc3e7 100644
--- a/game_manager_frame.php
+++ b/game_manager_frame.php
@@ -87,7 +87,7 @@ if (!get_autologin_state() || (($user_data["privilege"] !== PRIVILEGE_CREATOR) &
                         <td><label for="time_limited">Időkorlátos:</label></td>
                         <td>
                             <input type="checkbox" id="time_limited" oninput="handle_time_limit_chkbox()">
-                            <input type="time" id="time_limit" step="1">
+                            <input type="text" pattern="(([01][0-9])|([2][0-3])):[0-5][0-9]:[0-5][0-9]" id="time_limit">
                         </td>
                     </tr>
                     <tr>
diff --git a/group_manager_frame.php b/group_manager_frame.php
index d71650d..9a95a1f 100644
--- a/group_manager_frame.php
+++ b/group_manager_frame.php
@@ -56,6 +56,8 @@ if (!get_autologin_state() || ($user_data["privilege"] !== PRIVILEGE_QUIZMASTER)
                 <td><label for="group_owner">Tulajdonos:</label></td>
                 <td><input type="text" id="group_owner"></td>
             </tr>
+        </table>
+        <table id="group_editor_additional_fields">
             <tr>
                 <td><label for="group_editors">Szerkesztők:</label></td>
                 <td><input type="text" id="group_editors"></td>
diff --git a/groupmgr.php b/groupmgr.php
index 729f239..bb467a6 100644
--- a/groupmgr.php
+++ b/groupmgr.php
@@ -6,12 +6,12 @@ require_once "usermgr.php";
 
 $groupdb = new \SleekDB\Store(GROUPDB, DATADIR, ["timeout" => false]);
 
-function create_group(string $groupname, string $owner, string $description = "", array $editors = []): bool
+function create_group(string $groupname, string $owner, string $description = ""): bool
 {
     global $groupdb;
 
     // test name uniqueness
-    $unique = clear_unique_in_siblings($groupname);
+    $unique = manage_unique_in_siblings(0, $groupname);
 
     // initialize group data
     $group_data = [
@@ -19,7 +19,7 @@ function create_group(string $groupname, string $owner, string $description = ""
         "unique" => $unique,
         "owner" => $owner,
         "description" => $description,
-        "editors" => $editors,
+        "editors" => [],
         "users" => [],
         "games" => []
     ];
@@ -122,11 +122,11 @@ function search_groups(string $needle): array
     return $results;
 }
 
-function clear_unique_in_siblings($groupname): bool
+function manage_unique_in_siblings(int $current_gid, $groupname): bool
 {
     // make test on name uniqueness
     global $groupdb;
-    $twins = $groupdb->findBy(["groupname", "=", "$groupname"]);
+    $twins = $groupdb->findBy([["groupname", "=", "$groupname"], "AND", ["_id", "!=", $current_gid]]);
     $unique = count($twins) == 0;
     if (count($twins) === 1) { // if fails, then also indicate in the original group that its name is no longer unique
         $twins[0]["unique"] = false;
diff --git a/interface.php b/interface.php
index a5b87d2..7fc3f24 100644
--- a/interface.php
+++ b/interface.php
@@ -268,14 +268,14 @@ switch ($action) {
             if ($groupname != "") {
                 switch ($action) {
                     case "create_group":
-                        create_group($groupname, $owner, $description, $editors);
+                        create_group($groupname, $owner, $description);
                         break;
                     case "update_group":
                         {
                             $gid = $_REQUEST["id"];
                             $group = get_group($gid);
                             if (count($group) !== 0) {
-                                $group["unique"] = clear_unique_in_siblings($groupname); // manage unique flag in case of renaming
+                                $group["unique"] = manage_unique_in_siblings($gid, $groupname); // manage unique flag in case of renaming
                                 $group["groupname"] = $groupname;
                                 $group["description"] = $description;
                                 $group["editors"] = array_intersect($editors, $group["users"]); // a user cannot be an editor if not part of the group
diff --git a/js/gamemgr.js b/js/gamemgr.js
index ba09e1d..f53e16d 100644
--- a/js/gamemgr.js
+++ b/js/gamemgr.js
@@ -95,6 +95,10 @@ function create_edit_game(game = null) {
 
     submit_btn.onclick = () => {
         let game_name = document.getElementById("game_name").value.trim();
+        if (updating && time_limitedChk.checked && time_limitF.validity.patternMismatch) {
+            alert("Hibás időformátum!")
+            return;
+        }
         if (game_name !== "") {
             let reqData = {
                 name: game_name,
diff --git a/js/groupmgr.js b/js/groupmgr.js
index 892993e..c489886 100644
--- a/js/groupmgr.js
+++ b/js/groupmgr.js
@@ -49,6 +49,7 @@ function create_edit_group(group = null) {
         group_ownerF.readOnly = true;
         group_editorsF.value = "";
         group_membersF.value = "";
+        hide("group_editor_additional_fields");
     } else { // update and existing one
         groupnameF.value = group["groupname"];
         group_descriptionF.value = group["description"];
@@ -57,6 +58,7 @@ function create_edit_group(group = null) {
         group_ownerF.readOnly = false;
         group_editorsF.value = group["editors"].join(", ");
         group_membersF.value = group["users"].join(", ");
+        show("group_editor_additional_fields");
     }
 
     submit_btn.onclick = () => {
diff --git a/usermgr.php b/usermgr.php
index 1062229..bf009fa 100644
--- a/usermgr.php
+++ b/usermgr.php
@@ -9,7 +9,7 @@ const PRIVILEGE_PLAYER = "player";
 const PRIVILEGE_CREATOR = "creator";
 const PRIVILEGE_QUIZMASTER = "admin"; // TODO: refactor!
 
-function add_user(string $nickname, string $password, string $realname, array $groups = [], string $privilege = PRIVILEGE_PLAYER): bool
+function add_user(string $nickname, string $password, string $realname, array $groupids = [], string $privilege = PRIVILEGE_PLAYER): bool
 {
     global $userdb;
     if (count(get_user($nickname)) != 0) { // user exists
@@ -20,9 +20,12 @@ function add_user(string $nickname, string $password, string $realname, array $g
         "nickname" => $nickname,
         "password" => password_hash($password, PASSWORD_DEFAULT),
         "realname" => $realname,
-        "groups" => $groups,
+        "groups" => $groupids,
         "privilege" => $privilege
     ];
+    foreach ($groupids as $groupid) {
+        change_group_user_assignments($groupid, $nickname, null);
+    }
     $userdb->insert($user_data);
     return true; // user registration successful
 }