Based on the provided hint and the available files, here are potential issues identified in the dataset files regarding the missing task file as mentioned in `DATASET_SUBMISSION.md`:

1. **Issue: Missing task file**
   - **Evidence**: There is no mention or presence of a task file in the provided dataset files (`MUTAG.ipynb`, `LICENSE`, `metadata.json`, `README.md`, and `DATASET_SUBMISSION.md`).
   - **Description**: According to the `DATASET_SUBMISSION.md` instructions, a task file should be included in the dataset submission. This task file appears to be missing from the current submission. The absence of this file may lead to incomplete information about the dataset's purpose and the specific tasks it supports.

2. **Issue: Lack of explicit reference to task file requirements in `metadata.json`**
   - **Evidence**: The content of `metadata.json` does not include any reference or metadata field regarding the task file.
   - **Description**: The `metadata.json` file should ideally contain a field that references the task file, indicating its presence and providing metadata about its content. This omission suggests that the dataset metadata is incomplete and does not adhere to the submission guidelines.

3. **Issue: Incomplete task information in `README.md`**
   - **Evidence**: The `README.md` file lacks detailed information about the task file.
   - **Description**: The README should provide an overview of all included files, including the task file, to guide users on how to utilize the dataset effectively. The absence of this information can lead to confusion and difficulty in understanding the dataset's application.

### Summary
These issues highlight the missing task file, lack of metadata referencing the task file, and insufficient documentation in the README. To resolve these, ensure the task file is included, update the `metadata.json` to reference the task file, and enhance the README with relevant task information.