by Gus Hagelberg.
I just had trouble migtrating from moodle 1.9.19 to 2.3. The system check page said I had moodle 1.9.18 installed and needed 2.2. I had successfully completed the migration previously to moodle 2.2.
I then reverted to moodle 2.2 and the migration was successful. Everything else was the same, only my moodle core was 2.2 instead of 2.3.