If documents at Liferay Portal have not extension, LR Sync download it but it does not add file extension at Windows, so downloaded files can not be used by final user (windows does not know which application to use)
Steps to reproduce
1. Create Microsoft Word "test.docx" file.
2. At Liferay Portal, open Document and Media
3. Upload created "test.docx" file and fill its title as "test"
4. Install Liferay Sync and configure it to replicate the Site where "test.docx" file is stored
5. Sync downloads test file but without extension
6. User cannot open at windows because it has no extension
7. Additionally, If user rename the file adding the extension, it will be also added at server level "test" => "test.docx"