Error importing a course in Moodle 4.5.7

Hi!!

I'm using Moodle 4.5.7. When I try to copy a course (import it), it gets stuck and throws the error 

Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator at webmaster@localhost to inform them of the time this error occurred, and the actions you performed just before this error.
More information about this error may be available in the server error log.

This only happens in some courses, not all. If I copy it without the question bank, I don't have any problems, but it fails when I add it.

Thanks