>xxx.dbf is not a table

Either the zipper ended with errors, or the number of records changed during the zip, or something else happened. The expected number of records should be in the header, and the latest records would be at the end of the file. Since any zipper reads the file sequentially, and the table may have been open while zipping, the header at the time it was zipped had recorded fewer records than there may have been by the end of zipping. So the unpacked table has more records than its header shows - error sufficient to have it "not a table".

Or it may be something worse, I wouldn't know.