Docker can't find file (and it exists)

I am doing a project in Django, I use PyCharm in Windows 8.1. To start the web server and the database I use Docker installed on Debian (Linux) through a virtual machine (do not install Windows Docker for compatibility problems).

Upon entering the virtual machine, I mount the window folder on that machine:

mount.vboxsf csuperior /mnt/csuperior

I start the web container and db from the virtual machine and when I want to insert a breakpoint in the IDE, I get the following warning:

pydev debugger: warning: trying to add breakpoint to file that does not exist: /mnt/csuperior/reunion/views.py (will have no effect)

The strange thing is that the file exists and the path is correct. In fact I can modify it and the changes take effect.

To configure the debug I followed the following tutorial: Remote Debugging with PyCharm | PyCharm Documentation(without the SFTP part, since the files are copy when I load the folder). In the “path mapping” I use the same folders as in the mount.vboxsf.