Happen to be working with a Moodler who does same process ... backup no user, restore to new site.
On his site/hosting, mod_security is installed and active.
The error you are seeing indicates, obviously, cannot finish ... something interrupted the process ... not serious enough to crash Moodle, but serious enough to either kill a backup or complete it with missing parts/pieces. But what? I know not!
There is a command line utility (swiss army knife type like that of drush for Drupal sites) called moosh.
Works well ... on Linux.
The file have attached indicates that restore was successful ... it reached stage 1000.
There shouldn't be a 'matching' directory by "b26146b9868f832de5b5fdef60c81395" in there ... the last two actions is to ***copy*** (note that is copy NOT move) the backup file to configured destination directory ***AND*** then destroy the temp directory being used to build the backup file.
So, sorry, no clue in that .log file. As I tried to explain, the log file means something to coders ... hard core coders ... but not to me ... I asked one time in these forums what the numbers meant and if they were tied to a process for a part/piece of making the backup file. Don't recall getting any response, but then again, if there was, I might not have understood it.
It's only by observing the process that I've concluded that a stage ID number IS associated with making a backup of oh say 'activites and resources' (mods) ... you will see an xml file ... road map to activities directory. A files.xml ... road map to files in files directory but not by humanly recognizable names .. but, rather, built the same way files in moodledata/filedir are stored.
Now if you've created your own program, suggest maybe comparing what you've done to what Moosh does.
Too bad moodle doesn't have a 'restore.php' script in admin/cli/ that works like backup.php.
But, that's where moosh comes in.
There are 44 contributors to moosh
Maybe by reaching out to one of them ... the lead ... you could shave off hours and hours ... and get this done!
'spirit of sharing', Ken