10-17-2020 08:40 AM
The upgrade path from 8.4.7 and earlier version. you better revert to 8.4.7 or earlier release 8.4.x then upgrade to 8.5.1
10-27-2020 06:35 AM
But before downgrade, it is strongly recommended to backup the grid database. just in case your configuration in existing NIOS lost when you do revert to lower version.