I think the sample is out of date and may cause problems. There might be URL in the data that no longer exist.
I have two importers. The other CSV 2 POST and it is more advanced. Both are being updated to 8.0.0 and the updates bring lots of changes. CSV 2 POST was first and almost done. I'm hoping ECI is updated before end of April.
I'm taking a new approach with the sample files by hosting it on Google Documents with public access. There are links from the public to visit them plus links to download. The idea is to ensure while testing we're all working with the same data. So that issue is being addressed already. I think we should be able to use the spreadsheets and .csv examples in CSV 2 POST with ECI without it being an issue.
"Are you sure you want to do this?" could be a lot of things WordPress, mostly nonce security though. I would normally offer to get stuck in but in 2-3 weeks I'm updating it anyway. That will take a couple of weeks.
If however you could indicate the specific forms/screens you used it may be enough information to help me deliver a fix soon.