Calculating and Updating Inputs on the fly

Hi. Im working on trying to get an invoicing system setup on a test app (more for learning) and I'm having an issue with the repeater field updating the subtotal input and the invoice_total, but also the discount. Theres an odd issue where the repeater returns an odd figure to the subtotal and then If i update anything else it disapears and throws an error saying that subtitle is empty. Any help or info would be great, cheers

Heres the resource code:

Section::make('Service/Product details')
                    ->description('Details on the quantity, pricing and total costs.')
                    ->columns(2)
                    ->schema([

                        Forms\Components\Repeater::make('items')
                            ->label('Invoice items')
                            ->columnSpanFull()
                            ->relationship()
                            ->schema([
                                Forms\Components\TextInput::make('description')
                                    ->required()
                                    ->columnSpan(3),

                                Forms\Components\TextInput::make('price')
                                    ->numeric()
                                    ->inputMode('decimal')
                                    ->required()
                                    ->live()
                                    ->afterStateUpdated(function (Get $get, Set $set, $state) {
                                        // Calculate total when price is updated
                                        $qty = $get('qty'); // Get current qty
                                        $set('total', $state * $qty); // Update total
                                    })
                                    ->prefix('£'),

                                Forms\Components\TextInput::make('qty')
                                    ->numeric()
                                    ->required()
                                    ->live()
                                    ->afterStateUpdated(function (Get $get, Set $set, $state) {
                                        // Calculate total when qty is updated
                                        $price = $get('price'); // Get current price
                                        $set('total', $price * $state); // Update total
                                    }),

                                Forms\Components\TextInput::make('total')
                                    ->label('Total')
                                    ->numeric()
                                    ->inputMode('decimal')
                                    ->disabled() // Make it read-only
                                    ->dehydrated()
                                    ->prefix('£'), // Prevent it from being saved directly
                            ])
                            ->afterStateUpdated(function (Get $get, Set $set) {
                                // Calculate the invoice total whenever items change
                                $items = $get('items');
                                $invoiceTotal = collect($items)->sum('total');
                                $set('subtotal', number_format($invoiceTotal, 2));
                            })
                            ->live()
                            ->addActionLabel('Add invoice item')
                            ->columns(6),

                        Grid::make(1)
                            ->schema([
                                Forms\Components\TextInput::make('subtotal')
                                    ->numeric()
                                    ->live()
                                    ->inputMode('decimal')
                                    ->disabled()
                                    ->dehydrated()
                                    ->default(0)
                                    ->prefix('£'),

                                Forms\Components\TextInput::make('discount')
                                    ->label('Discount')
                                    ->numeric()
                                    ->reactive()
                                    ->inputMode('decimal')
                                    ->default(0)
                                    ->suffix('%')
                                    ->afterStateUpdated(function (Get $get, Set $set, $state) {
                                        $subtotal = $get('subtotal');
                                        $discount = $state / 100;
                                        $total = $subtotal - ($subtotal * $discount);
                                        $set('invoice_total', number_format($total, 2));
                                    }),

                                Forms\Components\TextInput::make('invoice_total')
                                    ->label('Invoice Total')
                                    ->numeric()
                                    ->live()
                                    ->inputMode('decimal')
                                    ->disabled()
                                    ->dehydrated()
                                    ->default(0)
                                    ->prefix('£'),
                            ])->columnStart(2),

                    ]),