> For AI agents: the complete documentation index is available at https://gultyayev.github.io/ngx-virtual-dnd/llms.txt, the full documentation bundle is available at https://gultyayev.github.io/ngx-virtual-dnd/llms-full.txt.

# Troubleshooting

Most problems come from one of the [rules that fail silently](https://gultyayev.github.io/ngx-virtual-dnd/guide/essentials/core-concepts.md#rules-that-fail-silently). Run the app in dev mode first: several of them log a console warning there.

| Symptom                                                                          | Likely cause and fix                                                                                                                                              |
| -------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Nothing drags; the console mentions a missing group                              | No group resolved. Add `vdndGroup` and declare the item template inside it.                                                                                       |
| The list area is empty or 0 px tall                                              | The list has no height. Set `containerHeight` or a CSS height on the scrolling element.                                                                           |
| Dragging works, but nothing follows the pointer                                  | `<vdnd-drag-preview />` is missing.                                                                                                                               |
| The drag cancels when the item scrolls out of view, or dynamic heights are wrong | The `vdndDraggable` ID differs from `itemIdFn` / `trackBy`. Use the same string in both places.                                                                   |
| Drops land a row or more off, worse further down the list                        | Rows are not exactly `itemHeight` tall. Fix the row height (borders and padding included) or turn on `dynamicItemHeight`.                                         |
| Items in other lists disappear while dragging                                    | Draggable IDs are duplicated across lists. Make them unique app-wide.                                                                                             |
| Items cannot be dropped into another list                                        | The lists are in different groups, or the target list has no `(drop)` handler.                                                                                    |
| `(drop)` fires but the arrays do not change                                      | The keys passed to `moveItem()` do not match the `droppableId`s.                                                                                                  |
| A gap stays where the dragged item was                                           | `vdndDraggable` is on a nested element. Move it to the template's root element.                                                                                   |
| A custom control inside a row starts a drag instead of responding                | Native buttons and inputs are already excluded. For other controls, add the `no-drag` class to the control (it covers everything inside it), or use `dragHandle`. |
| The preview loses its styling                                                    | The styles rely on ancestor selectors, and the preview is rendered under `<body>`. Target the preview's own classes.                                              |
| Drops land in the wrong list where two lists overlap                             | Hit-testing is geometric. See [Known limitations](https://gultyayev.github.io/ngx-virtual-dnd/guide/more/limitations.md#hit-testing).                             |

Still stuck? Check the [FAQ](https://gultyayev.github.io/ngx-virtual-dnd/guide/more/faq.md) and the [Known limitations](https://gultyayev.github.io/ngx-virtual-dnd/guide/more/limitations.md), or [open an issue](https://github.com/gultyayev/ngx-virtual-dnd/issues) with a minimal reproduction.