I think I've found the way the bug works, and some clue about why it could happen.
If I create a new user, as Apple Support suggested me, everything works.
But with my current user, I cannot open some files when the current folder (a folder that existed before Ventura 13.1) has some regional character on it. I'm Spanish, so my folders have á, é, í, ó, ú, ñ, etc in their names. For example: "Descripción del proceso".
If I try to open a file inside a folder with those characters using double click, the app won't open them.
BUT if I rename that folder even using the same characters, IT WORKS. I mean, the previous name was "Descripción del proceso". If I rename the folder replacing the "ó" with another "ó" (same character, so the folder still is named "Descripción del proceso"), now it works!
It would seem that Ventura can't recognize UNICODE characters (or something similar) that where typed before Ventura 13.1 (or Ventura 13, because I suffered errors opening files before). But if I type the characters again, Ventura transforms it to a coding that it can understand.
I've written this to @AppleSupport on Twitter, so I hope they finally acknowledge the bug, because it's a really big problem. As you can imagine, I have tons of files and folders with those regional characters that worked before Ventura, and I can't rewrite all of them.
I have by no means made a thorough test about this, so surely there's more I've missed, but I hope this can be useful to someone (and to someone with more technical knowledge)