Inserted Attachments are corrupt

Issue

You insert attachments, then you export them, and you try to open them but it doesn't allow you to do so and the weight is excessively less than what you uploaded it.

Cause

There is a bug that is caused because bulk API is not compatible with "Related objects" including Attachments objects.

Solution

There is an internal ticket created and dataloader.io engineering team will fix this issue in a future release.

Alternative solution

For the time being, please, use only the batch API option for Attachments tasks.
You can select it in the last step of the task wizard.