We've successfully migrated a light weight project (size: 1 MB) from JIRA on-prem to JIRA cloud site and we don't had any error log. But in destination cloud site, Projects window listing the migrated project but when clicking on the project, it doesn't show any single issue related to the project.
NOTE: In audit logs (cloud site), we could see the project's users/groups/WF/CF are created .