Changing these parameters:
MAX_ASSET_UPLOAD_FILE_SIZE_IN_MB = 400
STUDENT_FILEUPLOAD_MAX_SIZE = 400 * 1000 * 1000 # 430 MB
in cms/envs/common.py changes the size of this restriction, making available the upload of larger files.
In previous versions of the application (Dogwood, Bitnami) this worked fine, but in this one something crashes.
As it seems the limitation of the files is intentional: https://groups.google.com/forum/#!topic/edx-code/8MwhSbP_R4s
Apparently any file uploaded via this section is stored in the file system. Serving this files may overload the server. So, the correct option here is using a third part storage.
Thank yo so much for your help!