Hi
Firstly this plugin does not have a feature for thumbnails yet a.k.a featured images. I’ve had comments like this on my other plugins that make no sense at all, as if someone is trying to damage the plugins reputation without actually taking the time to try the plugin. The damage was done and I want to protect this new plugin so I’ll be keeping my eye on this post.
Please provide more information if you feel I am wrong, otherwise I will have to make a request for this post to be removed.
The way the plugin operates should not cause data in two or more records to be mixed up to create one post either. It queries the import data in the project database table for a single record, then uses all the data in that record to create post. When you say it has wrong feature images, it suggests it is using data from more than one record. Even when featured image feature is added and it will be soon. It would be a hard bug to occur.
This plugins author is Zara Walsh and I provide technical support on it. Maybe that will help clear a confusion up.