How to save custom field data when deploy candidate (create new bench)

I have custom field data added manually by the client, but when i update code and rebuild and deploy new bench to that site. That data is lost. Any solution?

No files, tests, or entry points are named. Start by reproducing the loss of manually added custom field data when code is updated and a new bench is rebuilt and deployed, then trace how site data is persisted across that operation. Done means the expected preservation behavior is established and verified with a regression check.

Written by the indexing model from the issue text.