diff --git a/admin/inc/class.admin_config.inc.php b/admin/inc/class.admin_config.inc.php
index 6db4049e5b..ae38805f4d 100644
--- a/admin/inc/class.admin_config.inc.php
+++ b/admin/inc/class.admin_config.inc.php
@@ -291,7 +291,7 @@ class admin_config
 		// make everything readonly and remove save/apply button, if user has not rights to store config
 		if ($GLOBALS['egw']->acl->check('site_config_acce',2,'admin'))
 		{
-			$readonlys[__ALL__] = true;
+			$readonlys['__ALL__'] = true;
 			$readonlys['cancel'] = false;
 		}
 
diff --git a/api/src/Accounts.php b/api/src/Accounts.php
index f7cc06c5ae..2ec473a64c 100644
--- a/api/src/Accounts.php
+++ b/api/src/Accounts.php
@@ -612,6 +612,20 @@ class Accounts
 			$account['account_firstname'] , $account['account_lastname'], $account_id);
 	}
 
+	/**
+	 * Return formatted username for Links, does NOT throw if $account_id is not int
+	 *
+	 * @param $account_id
+	 */
+	static function title($account_id)
+	{
+		if (empty($account_id) || !is_numeric($account_id) && !($id = self::getInstance()->name2id($account_id)))
+		{
+			return '#'.$account_id;
+		}
+		return self::username($id ?? $account_id);
+	}
+
 	/**
 	 * Format an email address according to the system standard
 	 *
diff --git a/api/src/Link.php b/api/src/Link.php
index 40a3bafeda..f86e96fd36 100644
--- a/api/src/Link.php
+++ b/api/src/Link.php
@@ -154,7 +154,7 @@ class Link extends Link\Storage
 			'name' => 'Accounts',
 			'icon' => 'addressbook/accounts',
 			'query' => 'EGroupware\\Api\\Accounts::link_query',
-			'title' => 'EGroupware\\Api\\Accounts::username',
+			'title' => 'EGroupware\\Api\\Accounts::title',
 			'view' => array('menuaction'=>'addressbook.addressbook_ui.view','ajax'=>'true'),
 			'view_id' => 'account_id'
 		),
@@ -914,7 +914,12 @@ class Link extends Link\Storage
 				}
 				else
 				{
-					$title = self::title($app,$id);	// no titles method --> fallback to query each link separate
+					try {
+						$title = self::title($app, $id);    // no titles method --> fallback to query each link separate
+					}
+					catch (\Throwable $e) {
+						$title = lang('Error').': '.$e->getMessage();
+					}
 				}
 			}
 			$titles[$id] = $title;
diff --git a/api/src/Sharing.php b/api/src/Sharing.php
index 7962a0ab4b..13640b379b 100644
--- a/api/src/Sharing.php
+++ b/api/src/Sharing.php
@@ -396,7 +396,7 @@ class Sharing
 		$class = strpos($status, '404') === 0 ? 'EGroupware\Api\Exception\NotFound' :
 			(strpos($status, '401') === 0 ? 'EGroupware\Api\Exception\NoPermission' :
 				'EGroupware\Api\Exception');
-		throw new $class($message, $status);
+		throw new $class($message, (int)$status);
 	}
 
 	/**
diff --git a/calendar/inc/class.calendar_so.inc.php b/calendar/inc/class.calendar_so.inc.php
index c38081cd7c..d8a19748f1 100644
--- a/calendar/inc/class.calendar_so.inc.php
+++ b/calendar/inc/class.calendar_so.inc.php
@@ -1663,6 +1663,14 @@ ORDER BY cal_user_type, cal_usre_id
 				// check if recurrence enddate was adjusted
 				if(isset($event['recur_enddate']))
 				{
+					if (is_object($event['recur_enddate']))
+					{
+						$event['recur_enddate'] = Api\DateTime::user2server($event['recur_enddate'], 'ts');
+					}
+					if (is_object($old_repeats['recur_enddate']))
+					{
+						$old_repeats['recur_enddate'] = Api\DateTime::user2server($old_repeats['recur_enddate'], 'ts');
+					}
 					// recurrences need to be truncated
 					if((int)$event['recur_enddate'] > 0 &&
 						((int)$old_repeats['recur_enddate'] == 0 || (int)$old_repeats['recur_enddate'] > (int)$event['recur_enddate'])
diff --git a/calendar/inc/class.calendar_uiforms.inc.php b/calendar/inc/class.calendar_uiforms.inc.php
index 9f5359cb66..37b047e681 100644
--- a/calendar/inc/class.calendar_uiforms.inc.php
+++ b/calendar/inc/class.calendar_uiforms.inc.php
@@ -55,7 +55,7 @@ class calendar_uiforms extends calendar_ui
 	/**
 	 * default locking time for entries, that are opened by another user
 	 *
-	 * @var locktime in seconds
+	 * @var int lock time in seconds
 	 */
 	var $locktime_default=1;
 
@@ -262,7 +262,7 @@ class calendar_uiforms extends calendar_ui
 			);
 		}
 
-		return array(
+		$ret = array(
 			'participant_types' => $participant_types,
 			'participants' => $participants,
 			'owner' => $owner,
@@ -278,6 +278,7 @@ class calendar_uiforms extends calendar_ui
 			'videoconference' => !empty($_GET['videoconference']),
 			'##notify_externals' => !empty($_GET['videoconference']) ? 'yes' : $this->cal_prefs['notify_externals'],
 		);
+		return $ret;
 	}
 
 	/**
@@ -1872,7 +1873,7 @@ class calendar_uiforms extends calendar_ui
 
 			if ($event['recur_type'] != MCAL_RECUR_NONE)
 			{
-				$readonlys['recur_exception'] = !count($content['recur_exception']);	// otherwise we get a delete button
+				$readonlys['recur_exception'] = empty($content['recur_exception']);	// otherwise we get a delete button
 				//$onclick =& $etpl->get_cell_attribute('button[delete]','onclick');
 				//$onclick = str_replace('Delete this event','Delete this series of recuring events',$onclick);
 			}
@@ -2843,7 +2844,7 @@ class calendar_uiforms extends calendar_ui
 		#error_log(__METHOD__.print_r($content,true));
 		if (is_numeric($cal_id = $content ? $content : $_REQUEST['cal_id']))
 		{
-			if (!($ical =& $boical->exportVCal(array($cal_id),'2.0','PUBLISH',false)))
+			if (!($ical = $boical->exportVCal(array($cal_id),'2.0','PUBLISH',false)))
 			{
 				$msg = lang('Permission denied');
 
@@ -2872,7 +2873,7 @@ class calendar_uiforms extends calendar_ui
 			}
 			else
 			{
-				$ical =& $boical->exportVCal($events,'2.0','PUBLISH',false);
+				$ical = $boical->exportVCal($events,'2.0','PUBLISH',false);
 				Api\Header\Content::type($content['file'] ? $content['file'] : 'event.ics','text/calendar',bytes($ical));
 				echo $ical;
 				exit();
diff --git a/importexport/inc/class.importexport_export_csv.inc.php b/importexport/inc/class.importexport_export_csv.inc.php
index aa3a8e0aee..b143d53346 100644
--- a/importexport/inc/class.importexport_export_csv.inc.php
+++ b/importexport/inc/class.importexport_export_csv.inc.php
@@ -387,18 +387,16 @@ class importexport_export_csv implements importexport_iface_export_record
 				$record->$name = '';
 			}
 		}
-		foreach($fields['select-account'] ?? [] as $name) {
+		foreach($fields['select-account'] ?? [] as $name)
+		{
 			// Compare against null to deal with empty arrays
-			if ($record->$name !== null) {
-				if(is_array($record->$name)) {
-					$names = array();
-					foreach($record->$name as $_name) {
-						$names[] = Api\Accounts::username($_name);
-					}
-					$record->$name = implode(', ', $names);
-				} else {
-					$record->$name = Api\Accounts::username($record->$name);
+			if ($record->$name !== null)
+			{
+				$names = array();
+				foreach((array)$record->$name as $_name) {
+					$names[] = Api\Accounts::title((int)$_name ?: $_name);
 				}
+				$record->$name = implode(', ', $names);
 			}
 			else
 			{