If a class has plugins and the deploy mode is set to developer the ObjectManager is supposed to generate an Interceptor of the class as needed. That's what happens when running `bin/magento setup:di:compile`.

In my case some Inteceptors are not generated even tho the class has at least one plugin.

I'm trying to add a plugin for a third party class. `di.xml` and the `after` method are declared correctly and the target method is called. Due to the missing Interceptor the plugin isn't executed.

If I run `bin/magento setup:di:compile` the Interceptor is generated and the plugin works as intended.

I tried to debug into `\Magento\Framework\Interception\ObjectManager\Config\Developer::getInstanceType` but here I don't get an instance of the class I target with the plugin.

Any ideas what the problem could be?

**Update:**  

I've debugged into the `index.php` and checked the state of `$app`. `_appMode` is set to developer. So I don't think the app mode is overwritten somewhere.