by Ken Task.
Sorry, no suggestion yet, but a question and a thought ...
What are the exact moodle versions of the 2 sites?
from code/ directory:
fgrep '$release' version.php
Thought? if restoring to a 4.1.highest of Moodle, there is now a 'restore_backup.php' script in admin/cli/ of 4.1 code.
'SoS', Ken