Limitations

FTP is a relatively fragile protocol, so it comes with some limitations which are also present in FileZilla.

FileZilla ignores leading space of filename or directory

This happens on FTP servers not supporting the MLSD command. On those servers FileZilla falls back to LIST. Unfortunately the listing format returned by LIST is not standardised. It is impossible to distinguish leading spaces from padding. To solve this issue, simply upgrade to a modern server supporting the MLSD command or refrain from using leading spaces.

Download process goes beyond 100%

Some FTP servers like Microsoft IIS as FTP server have a severe bug. They advertise resume support and accept the resume command, but instead of resuming, they send the complete file again. Unfortunately this cannot be detected client-side. But be aware that there are valid cases in which a transfer can be larger than the reported file size, for example if new data is appended to the file while it is being downloaded (like log files).