diff --git a/system/src/Grav/Framework/Flex/FlexForm.php b/system/src/Grav/Framework/Flex/FlexForm.php
index b679f5ce1..6ded34590 100644
--- a/system/src/Grav/Framework/Flex/FlexForm.php
+++ b/system/src/Grav/Framework/Flex/FlexForm.php
@@ -20,6 +20,7 @@ use Grav\Framework\Form\Traits\FormTrait;
 use Grav\Framework\Route\Route;
 use Twig\Error\LoaderError;
 use Twig\Error\SyntaxError;
+use Twig\Template;
 use Twig\TemplateWrapper;
 
 /**
@@ -277,7 +278,7 @@ class FlexForm implements FlexFormInterface
 
     /**
      * @param string $layout
-     * @return TemplateWrapper
+     * @return Template|TemplateWrapper
      * @throws LoaderError
      * @throws SyntaxError
      */
diff --git a/system/src/Grav/Framework/Flex/FlexIndex.php b/system/src/Grav/Framework/Flex/FlexIndex.php
index 29ac33bbc..8b96b4a9a 100644
--- a/system/src/Grav/Framework/Flex/FlexIndex.php
+++ b/system/src/Grav/Framework/Flex/FlexIndex.php
@@ -312,9 +312,10 @@ class FlexIndex extends ObjectIndex implements FlexCollectionInterface, FlexInde
         // Ordering can be done by using index only.
         $previous = null;
         foreach (array_reverse($orderings) as $field => $ordering) {
+            $field = (string)$field;
             if ($this->getKeyField() === $field) {
                 $keys = $this->getKeys();
-                $search = array_combine($keys, $keys);
+                $search = array_combine($keys, $keys) ?: [];
             } elseif ($field === 'flex_key') {
                 $search = $this->getFlexKeys();
             } else {
@@ -462,7 +463,7 @@ class FlexIndex extends ObjectIndex implements FlexCollectionInterface, FlexInde
             $first = reset($entries);
             if ($first) {
                 $keys = array_keys($first);
-                $keys = array_combine($keys, $keys);
+                $keys = array_combine($keys, $keys) ?: [];
             } else {
                 $keys = [];
             }
diff --git a/system/src/Grav/Framework/Flex/FlexObject.php b/system/src/Grav/Framework/Flex/FlexObject.php
index 5208fc196..01f45d079 100644
--- a/system/src/Grav/Framework/Flex/FlexObject.php
+++ b/system/src/Grav/Framework/Flex/FlexObject.php
@@ -31,6 +31,7 @@ use Psr\SimpleCache\InvalidArgumentException;
 use RocketTheme\Toolbox\Event\Event;
 use Twig\Error\LoaderError;
 use Twig\Error\SyntaxError;
+use Twig\Template;
 use Twig\TemplateWrapper;
 
 /**
@@ -391,7 +392,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
         }
 
         try {
-            $data = $cache ? $cache->get($key) : null;
+            $data = $cache && $key ? $cache->get($key) : null;
 
             $block = $data ? HtmlBlock::fromArray($data) : null;
         } catch (InvalidArgumentException $e) {
@@ -410,7 +411,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
         }
 
         if (!$block) {
-            $block = HtmlBlock::create($key);
+            $block = HtmlBlock::create($key ?: null);
             $block->setChecksum($checksum);
             if ($key === false) {
                 $block->disableCache();
@@ -434,7 +435,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
             $block->setContent($output);
 
             try {
-                $cache && $block->isCached() && $cache->set($key, $block->toArray());
+                $cache && $key && $block->isCached() && $cache->set($key, $block->toArray());
             } catch (InvalidArgumentException $e) {
                 $debugger->addException($e);
             }
@@ -541,7 +542,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
         $result = $this->getFlexDirectory()->getStorage()->replaceRows([$this->getStorageKey() => $this->prepareStorage()]);
 
         $value = reset($result);
-        $storageKey = key($result);
+        $storageKey = (string)key($result);
         if ($value && $storageKey) {
             $this->setStorageKey($storageKey);
             if (!$this->hasKey()) {
@@ -558,7 +559,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
             if (method_exists($this, 'clearMediaCache')) {
                 $this->clearMediaCache();
             }
-        } catch (InvalidArgumentException $e) {
+        } catch (\Exception $e) {
             /** @var Debugger $debugger */
             $debugger = Grav::instance()['debugger'];
             $debugger->addException($e);
@@ -586,7 +587,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
             if (method_exists($this, 'clearMediaCache')) {
                 $this->clearMediaCache();
             }
-        } catch (InvalidArgumentException $e) {
+        } catch (\Exception $e) {
             /** @var Debugger $debugger */
             $debugger = Grav::instance()['debugger'];
             $debugger->addException($e);
@@ -807,7 +808,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
 
     /**
      * @param string $layout
-     * @return TemplateWrapper
+     * @return Template|TemplateWrapper
      * @throws LoaderError
      * @throws SyntaxError
      */
diff --git a/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php b/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php
index b547cc227..cc460ccd0 100644
--- a/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php
+++ b/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php
@@ -128,7 +128,7 @@ abstract class AbstractFilesystemStorage implements FlexStorageInterface
             return $path;
         }
 
-        return (string) $locator->findResource($path) ?: $locator->findResource($path, true, true);
+        return (string)($locator->findResource($path) ?: $locator->findResource($path, true, true));
     }
 
     /**
diff --git a/system/src/Grav/Framework/Flex/Storage/FolderStorage.php b/system/src/Grav/Framework/Flex/Storage/FolderStorage.php
index 2304e8013..76397c235 100644
--- a/system/src/Grav/Framework/Flex/Storage/FolderStorage.php
+++ b/system/src/Grav/Framework/Flex/Storage/FolderStorage.php
@@ -455,6 +455,8 @@ class FolderStorage extends AbstractFilesystemStorage
     protected function initOptions(array $options): void
     {
         $extension = $this->dataFormatter->getDefaultFileExtension();
+
+        /** @var string $pattern */
         $pattern = !empty($options['pattern']) ? $options['pattern'] : $this->dataPattern;
 
         $this->dataFolder = $options['folder'];
diff --git a/system/src/Grav/Framework/Flex/Storage/SimpleStorage.php b/system/src/Grav/Framework/Flex/Storage/SimpleStorage.php
index 209ba3382..088b9527e 100644
--- a/system/src/Grav/Framework/Flex/Storage/SimpleStorage.php
+++ b/system/src/Grav/Framework/Flex/Storage/SimpleStorage.php
@@ -227,7 +227,12 @@ class SimpleStorage extends AbstractFilesystemStorage
         $keys = array_keys($this->data);
         $keys[array_search($src, $keys, true)] = $dst;
 
-        $this->data = array_combine($keys, $this->data);
+        $data = array_combine($keys, $this->data);
+        if (false === $data) {
+            throw new \LogicException('Bad data');
+        }
+
+        $this->data = $data;
 
         return true;
     }
diff --git a/tests/phpstan/phpstan.neon b/tests/phpstan/phpstan.neon
index e8e24ff51..29781281b 100644
--- a/tests/phpstan/phpstan.neon
+++ b/tests/phpstan/phpstan.neon
@@ -41,14 +41,15 @@ parameters:
             message: '#Grav\\Common\\GPM\\Remote\\GravCore::__construct\(\) does not call parent constructor from Grav\\Common\\GPM\\Remote\\AbstractPackageCollection#'
             path: 'system/src/Grav/Common/GPM/Remote/GravCore.php'
 
+        # PSR-16 Exception interfaces do not extend \Throwable
+        - '#PHPDoc tag \@throws with type Psr\\SimpleCache\\(CacheException|InvalidArgumentException) is not subtype of Throwable#'
+        - '#expects Exception, Psr\\SimpleCache\\InvalidArgumentException&Throwable given#'
+
         # Needed: psr-17 (http-factories) support (through decorator or further investigations)
         -
             message: '#Call to an undefined static method Grav\\Framework\\Psr7\\Stream::create\(\)#'
             path: 'system/src/Grav/Framework/Form/FormFlashFile.php'
 
-        # PSR-16 Exception interfaces do not extend \Throwable
-        - '#PHPDoc tag \@throws with type Psr\\SimpleCache\\(CacheException|InvalidArgumentException) is not subtype of Throwable#'
-
         # Medium __call() methods
         - '#Call to an undefined method Grav\\Common\\Page\\Medium\\(\w*)Medium::#'