Error 500 out of the blue-Backoffice dead (php error?)

[Puriom]

Hello!
I was working with a mod's translation, on which I had worked before, and suddenly I've got a HTTP Error 500.

- From Plesk I renamed the mod, but nothing.

The logs:

 

Error message: GET /Backoffice/index.php?controller=AdminDashboard&token=3d12c6c29c57f3195cd3152dfadc491f HTTP/1.0

 

And excactly after it (next line):
mod_fcgid: stderr: PHP Fatal error: Cannot redeclare class Symfony\\Component\\DependencyInjection\\ContainerAwareInterface in /var/www/vhosts/21286914721.thesite.link/MYSITE.com/app/cache/prod/classes.php on line 6949

 

I don't know programming.

 

PS 1.7.2. My site has not its DNS set on the server yet.

ANY HELP PLEASE?

Thanks in advance

Edited August 8, 2017 by Puriom (see edit history)