If there are multiple tasks in a project that have the same name, when processing the CSV export of the project, it is impossible to know which parent task any subtasks belong to, as the only identifier given for a parent task is the parent task name.
Including columns for both the parent task name and parent task ID in the CSV export would help this deduplication. In the JSON data feed of a project, any parent task hash includes both the task ID and the task name - it would be great to add this to the CSV exports too.
Until/if that becomes available, consider the Asana2Go CSV - Detailed output which can be tweaked just by adding a few characters to include the parent GID in the meantime: