Laravel 5.5 throws ReflectionException CustomRequest Class doen't exist after upgrade from 5.4

I have recently upgraded Laravel to version 5.5 from 5.4, but whenever I send an API response to the server while updating or storing some information that uses custom requests, for example, book posts (BooksRequest), it throws an exception like the following:

ReflectionException
Class App\Http\Requests\Admin\BooksRequest does not exist

/home/gingern/Web/www/asiacrochet/vendor/laravel/framework/src/Illuminate/Routing/RouteSignatureParameters.php:25

in that part of file:

public static function fromAction(array $action, $subClass = null)
    {
        $parameters = is_string($action['uses'])
                        ? static::fromClassMethodString($action['uses'])
                        : (new ReflectionFunction($action['uses']))->getParameters();
 
        return is_null($subClass) ? $parameters : array_filter($parameters, function ($p) use ($subClass) {
            return $p->getClass() && $p->getClass()->isSubclassOf($subClass);
        });
    }

Before upgrading everything was working fine.

I've tried

composer dump-autoload -o

In vendor/composer/autoload_classmap.php there are no such classes. Update: I don't know how, but now there are needed classes in this file, for example:

'App\Http\Requests\Admin\BooksRequest' => $baseDir . '/app/Http/Requests/Admin/BooksRequest.php',

Part of my BooksRequest class:

<?php

namespace App\Http\Requests\Admin;

use Illuminate\Foundation\Http\FormRequest;

use Illuminate\Validation\Factory as ValidationFactory;

use Carbon\Carbon;
use Purifier;
use App\Book;
use App\Traits\RequestsExtraFunctions;

class BooksRequest extends FormRequest
{
    use RequestsExtraFunctions;

    public function __construct(ValidationFactory $validationFactory)
    {
        $this->setExtraImagesRules($validationFactory, 'App\Book');
    }

    public function authorize()
    {
        return true;
    }

    public function rules()
    {
        $id = (int)$this->route('book');

        $rules = [
            //some rules
        ];
        //some additional rules
        return $rules;
    }

    public function all()
    {
        $input = parent::all();
        //some manipulations on input
        return $input;
    }
}

Controller that uses BooksRequest:

<?php

namespace App\Http\Controllers\Admin;

use Illuminate\Http\Request;
use App\Http\Controllers\Controller;

use Illuminate\Support\Facades\Auth;
use Validator;

use App\Http\Requests\Admin\BooksRequest;
use App\Book;

class BooksController extends Controller
{
    public function store(BooksRequest $request)
    {
        $input = $request->all();  
    //some manipulations
        return redirect()->route('admin.books.index');     
    }

    public function update(BooksRequest $request, $id)
    {
        $book = Book::find($id);
    //some manipulations
        return redirect()->route('admin.books.edit', $book->id)->with('status', trans('status.edit_success'));
    }
}

Also my problem looks similar to this question, but not exactly and answer didn't help https://laracasts.com/discuss/channels/laravel/laravel-51-throws-reflectionexception-after-upgrade-from-50?page=1