diff --git a/lib/Cron/CronHelper.php b/lib/Cron/CronHelper.php
index c29c0edecb..63c45ebd21 100644
--- a/lib/Cron/CronHelper.php
+++ b/lib/Cron/CronHelper.php
@@ -186,20 +186,23 @@ class CronHelper {
       throw new \Exception(__('Site URL is unreachable.', 'mailpoet'));
     }
 
-    $scheme = '';
+    $callScheme = '';
     if (isset($parsedUrl['scheme']) && ($parsedUrl['scheme'] === 'https')) {
-      $scheme = 'ssl://';
+      $callScheme = 'ssl://';
     }
+
     // 1. if site URL does not contain a port, return the URL
     if (!isset($parsedUrl['port']) || empty($parsedUrl['port'])) return $siteUrl;
     // 2. if site URL contains valid port, try connecting to it
-    $fp = @fsockopen($scheme . $parsedUrl['host'], $parsedUrl['port'], $errno, $errstr, 1);
+    $urlHost = $parsedUrl['host'] ?? '';
+    $fp = @fsockopen($callScheme . $urlHost, $parsedUrl['port'], $errno, $errstr, 1);
     if ($fp) return $siteUrl;
     // 3. if connection fails, attempt to connect the standard port derived from URL
     // schema
-    $port = (strtolower($parsedUrl['scheme']) === 'http') ? 80 : 443;
-    $fp = @fsockopen($scheme . $parsedUrl['host'], $port, $errno, $errstr, 1);
-    if ($fp) return sprintf('%s://%s', $parsedUrl['scheme'], $parsedUrl['host']);
+    $urlScheme = $parsedUrl['scheme'] ?? '';
+    $port = (strtolower($urlScheme) === 'http') ? 80 : 443;
+    $fp = @fsockopen($callScheme . $urlHost, $port, $errno, $errstr, 1);
+    if ($fp) return sprintf('%s://%s', $urlScheme, $urlHost);
     // 4. throw an error if all connection attempts failed
     throw new \Exception(__('Site URL is unreachable.', 'mailpoet'));
   }
diff --git a/lib/Doctrine/Types/JsonType.php b/lib/Doctrine/Types/JsonType.php
index ea8932ad23..e4d46e0ad7 100644
--- a/lib/Doctrine/Types/JsonType.php
+++ b/lib/Doctrine/Types/JsonType.php
@@ -36,7 +36,7 @@ class JsonType extends Type {
       $value = stream_get_contents($value);
     }
 
-    $value = mb_convert_encoding($value, 'UTF-8', 'UTF-8'); // sanitize invalid utf8
+    $value = mb_convert_encoding((string)$value, 'UTF-8', 'UTF-8'); // sanitize invalid utf8
     $decoded = json_decode($value, true);
     $this->handleErrors();
     return $decoded;
diff --git a/lib/Form/Widget.php b/lib/Form/Widget.php
index 7f47071da1..c0136fe911 100644
--- a/lib/Form/Widget.php
+++ b/lib/Form/Widget.php
@@ -168,6 +168,7 @@ class Widget extends \WP_Widget {
       }
     </script>
     <?php
+    return '';
   }
 
   /**
diff --git a/lib/Models/Model.php b/lib/Models/Model.php
index 4cbdffb134..253efc1353 100644
--- a/lib/Models/Model.php
+++ b/lib/Models/Model.php
@@ -222,6 +222,10 @@ class Model extends \MailPoetVendor\Sudzy\ValidModel {
     }
   }
 
+  /**
+   * @return static
+   * @phpstan-ignore-next-line Our Model has incompatible return type with parent
+   */
   public function save() {
     $this->setTimestamp();
     $this->newRecord = $this->isNew();
@@ -387,7 +391,7 @@ class Model extends \MailPoetVendor\Sudzy\ValidModel {
 
   public function __set($name, $value) {
     $name = Helpers::camelCaseToUnderscore($name);
-    return parent::__set($name, $value);
+    parent::__set($name, $value);
   }
 
   public function __isset($name) {