Can't recommend changes (except forever upwards and that could lead to making server un-stable) without knowing more about why!!!
Since you say no errors in any error logs the only alternative is to investigate/explore what you can ... the moodledata/temp/backup/longfoldername/ contents.
What does one of those look like? List files please ... like all the .xml files ...
What is in the course? Like how many quizzes ... videos resources that reside in the moodle etc.