2. perform a full backup, download all backup files,
upload all backup files, rescan local folder, start migration.
as described in https://updraftplus.com/faqs/how-do-i-migrate-to-a-new-site-location/
the migration was interrupted, maybe by a plugin (maybe WP Cerber).
(You have exceeded the number of allowed login attempts. Please try again in ..)
the migration was incomplete, files were missing.
Could you try to reduce the backup archive split size further down? It appears that the backup gets timed out.
To do this, open the ‘expert settings’ section of the UpdraftPlus Settings tab, and find the ‘split backups every’ option. Set this to 25Mb, save your settings and run a new process.