Renaming FAT file in Explorer accepts backslash character in some cases

Usually file rename with backslash is rejected, but there are some cases where it causes strange results.
1) rename filename.txt into \filename.txt - file may disappear from view or remain with backslash while another file disappears, until view is refreshed
2) rename filename.txt into filename.t
- file is renamed to 'filename.' and further rename with Explorer fails (this is different than feature of Windows where file needs to be renamed with trailing dot to be made a hidden file without trailing dot, which works on ROS too). If then tried to do something with the file in cmd - there is file not found error.
3) rename with one backslash at the end. File icon turns into a folder - after view refresh, it becomes normal file with one extra character cut at the end from filename.
bootcd-r72030-dbg.iso, VirtualBox 5.0.20