Please make sure that there aren't any file with 0byte size within the .article zip file. Even if the .article zip file that you uploaded is 54kb, the contain of the zip file may contain 0byte size files.
10Ton, The .article file is actually compressed file of an index.html file, as well as other resources such as image, .js folder, fonts, and css files. You can use an Unarchiving utility such as The Unarchiver (one among many) to view the contents of the .article file. Then, as Mike said, remove any 0k files, and use the HTML Packager applet to recompress the .article file.