pywatchdog and pyinotify not detecting changes on files inside ftp created directories

Question

I have an application monitoring files sent to a FTP server (proftpd 1.3.5a). I am using pywatchdog to monitor file creation on FTP server root (app running locally), but under some very specific circumstance it does not issue a notification: when I create a new dir through ftp and, after that, create a file under this directory. The file creation/modification events are not caught!

In order to reproduce it in a simple way I've used pyinotify (0.9.6) itself and it looks like the problem comes from there. So, a simple way to reproduce the problem:

1. Install proftpd and pyinotify (python3) on the server with default settings
2. In the server, run the following command to monitor ftp root (recursive and autoadd turned on - considering user "user"): python3 -m pyinotify -v -r -a /home/user
3. In the client, create a sample.txt, connect in the ftp server and issue the following commands, in this order: mkdir dir_a cd dir_a put sample.txt
4. There will be no events related to sample.txt - neither create nor modify!

I've tried to remove the ftp factor from the issue by manually creating and moving directories inside the observed target and creating files inside these directories, but the issue does not happen - it all works smoothly.

Any help will be appreciated!