by Ken Task.
From the output of debug, looks like the backup file has the old assignments in it. Your newer system is set to use the newest 'assign' module.
If you can, turn on the old assignments mod (un-hide it). Restore the course.
Site admin menu should have a link to Assignment Upgrade Helper. Click that and upgrade all the assignments it can find to the new assign mod.
Once done, hide the old assignments again.
Go to the course you just restored an check out any one of the assignments there.
'spirit of sharing', Ken