In latest test build (as of 17th of may) When you quickly type a new name, using the export to CSV function, and then do not add ".csv" again after the newly named CSV file, you end up with a file named "filename.CVS". Seems like a typo.
If you just save with the default filename, which has the proper .cvs extension, then the file is immediately readable.
Changing extension back to "filename.csv" from "filename.cvs" makes file readable as well.
Awesome work on the new test build though.