As to my experiences, you need to clarify first whether the upgrade script encountered an error - so do not try to continue upon an error.
Switch all error reportings in config.inc.php to “on”, make backups of the original system, test the upgrade process on a separate development server where you can always delete the database, repopulate the db with an original sql backup dump, and then re-run the script until things run smoothly.
Taking for granted that you use the php-cli on the command-line - giving you more convenience and information about the system.
PS.: This was my error I stumpled upon in my install procedure: OJS3.2 Upgrade Error - Please help
Best
Klaus