«Recoverable Error: Argument 2 passed to Interceptor::___callParent() must be of the type array, object given»

The cause of this error is wrong return type of your before plugin: you must return result as array.
For example:

namespace Df\Framework\App;
use \Magento\Framework\App\ActionInterface;
use \Magento\Framework\App\RequestInterface;
class ActionInterfacePlugin {
	 * @param ActionInterface $subject
	 * @param RequestInterface $request
	 * @return RequestInterface
	public function beforeDispatch(ActionInterface $subject, RequestInterface $request) {
		return [$request];