The attached document is describing how to downgrade from 5.2.1.
The upgrade guide of 5.2.1 was described as follows.
From the 5.2.1 upgrade guide.
Downgrading from VDS TC 5.2.1
If you need to downgrade from VDS TC 5.2.1 to a previous version of VDS TC, please contact Cisco TAC.
Caution To be able to perform a roll back, you must perform this roll back within 7 days of the upgrade.
you can download the document in CCO.
http://www.cisco.com/c/dam/en/us/td/docs/video/videoscape/distribution_suite/vds/v5_2/VDS_TC_5_2_1_app_downgrade_guide.pdf