Why does an inertia route change?

Question

In a Laravel/Inertia application, I try to store vinylRecords.

Therefore I created a vinylRecords resource.

Route::resource('vinylRecords', VinylRecordController::class)->only(['index', 'create','store', 'edit', 'update']);

In the frontend, the store function looks like:

  methods: {
    submitForm() {
      this.$inertia.post(route("vinylRecords.store"), this.form, {
        onSuccess: (response) => {
          alert(Object.keys(response.props))
          this.form.reset();
        },
      });
    }
  },

Sometimes, the routing is right and the Laravel stores the new record. But most of time, Laravel redirects to the index method without storing the data.

The store method:

    public function store(StoreVinylRecordRequest $request)
    {
        $data = $request->validated();

        $record = VinylRecord::create($data);

        $record->labels()->sync($data['label_ids']);
        $record->styles()->sync($data['style_ids']);
        $record->specials()->sync($data['special_ids']);

        return Inertia::render('vinylRecord/index', [
            'records'   =>   VinylRecordResource::collection(VinylRecord::all()),
            'vinylRecordId' => $record->id
        ]);
    }

To solve the problem, I created a new controller with a new route to store the data:

Route::post('storeVinylRecord', [StoreVinylRecordController::class, 'store'])->name('storeVinylRecord');

But the problem was the same.

How is it possible, that the routing changes from one request to the other? Is there an big error in the code from my side?

Edited: Add the StoreVinylRecordRequest

    public function rules()
    {
        return [
            'artist' => 'required|string',
            'title' => 'required|string',
            'barcode' => 'nullable|integer',
            'genre_id' =>   'nullable|integer',
            'country' => 'nullable',
            'year' => 'nullable|integer',
            'label_ids' =>  'nullable',
            'style_ids' =>  'nullable',
            'special_ids' =>  'nullable',
            'thumb' =>  'nullable|string',
            'cover_image' =>  'nullable|string',
            'quantity'  =>  'nullable|integer',
            'speed' =>  'nullable|integer',
            'part_type' =>  'nullable|string',
            'storage_location' => 'nullable|string',
            'supplier_id' => 'nullable|in:suppliers,id',
            'purchasing_price' =>  'nullable|numeric',
            'selling_price' =>  'nullable|numeric',
        ];
    }