by Ken Task.
Whatever you tweaked upwards, nudge them a little higher!
For clues, inspect moodledata/temp/backup/ ... that's the location of a backup extracted for restore.
Your failed restores there will remain directories that were used ... sucessful restores have the directories they used erased with cron job/task for clean ups.
So directories that you see that look like a bunch of letters and numbers ... look in them ... you should see .xml files with related directories ... example: files.xml and a files directory.
Things that could take a lot of time ... quiz banks.
Show how large is the questions.xml file? Etc. Sorry .. no science to it ... just sluething.
'SoS', Ken