Migrate from Owncloud 9.1.8.2 fails

I have two running Owncloud systems which I’ve tried to migrate to Nextcloud using the manual migration process:
version 9,1,2,5 went beautifully
version 9,1,8,2 fails with the following error message when I run this command “sudo -u www-data php occ upgrade”:

An unhandled exception has been thrown:
OC\HintException: [0]: Downgrading is not supported and is likely to cause unpredictable issues (from 9.1.8.2 to 9.1.6.1) ()

I’ve followed the instructions on this page https://docs.nextcloud.com/server/12/admin_manual/maintenance/manual_upgrade.html and using the reference on this page https://docs.nextcloud.com/server/13/admin_manual/maintenance/migrating_owncloud.html
I’m trying to use the 10.0.x Nextcloud download as the first step.

Any thoughts? Please. Many thanks.

I would prefer a migration from oC 9.1 to NC 10 (or perhaps NC 11) rather than oC 10. Especially if you upgrade to the latest oC 10, there are likely to be some errors.

After each new version, all the migration procedures have to be reviewed, normally this should be done soon: