Hi,
I see you are using "Ftp Wait Mode".
This mode is used to wait for files which may not be present at the moment of the execution, with setting a number of file to wait or a timeout. The action will then wait for files, which can appear on the fly during the execution, until the timeout or number of files is reached.
In the first screenshot you provide,showing the process, you were waiting an infinite number of file, but with no timeout. Like Thomas said, it can lead to a process running indefinitely.
It looks like you only needed to retrieve files which are already present and existing in the folder.
If it is correct you don't need to use the "Ftp Wait Mode" or "FTP_NB_FILES" parameters.
For example, this should work to retrieve all the .txt files of a folder :