Traditionally, for all build versions of 2.5.xxx before 920, it was possible to revert the appliance to an earlier snapshot, as explained in the KB below. However, due to the major changes that were made to the underlying operating system of TPAM, it is not possible to revert the appliance to a previous version or to the factory default version after OSPatch_3106991 and the 2.5.920 upgrade have been applied.
Is it possible to downgrade or rollback a TPAM appliance? (208443)
https://support.oneidentity.com/tpam/kb/208443
PLEASE ENSURE THAT A FULL BACKUP IS CREATED AND STORED IN A SAFE LOCATION IMMEDIATELY AFTER THE 2.5.920 UPGRADE TO AVOID DATA LOSS IN THE EVENT OF A FAILURE.
If an appliance failure occurs on an appliance running 2.5.920, where the factory default image is a lower version, it will be necessary to process an RMA replacement for the affected appliance. Contact One Identity Support for assistance with this process.