by Ken Task.
A very old tracker issue
https://tracker.moodle.org/browse/MDL-23559
suggest your error related to language and characters in labels.
dolanguages.com isn't using https:// get a FireFox warning so think I"ll not view since you are having issues.
In dolanguages site, what languages have you installed? en is default, me thinks, but others?
The courses you are attempting to restore ... what language are they using?
When you restore one of those are you stepping through each screen in the restore process? Try that ... when it comes to the page showing the contents of the course to be restored, un-check any/all label resources.
Can you turn on debugging and share back what else moodle might tell you?
'SoS', Ken