I encountered the same issue, and submitted to ibm support, and per ibm development, they are going to fix this in 8.11. At the mean time they gave me an workaround which worked for us.
workaround steps provided by ibm development: ('test' is the instance id in our environment)
- Create a new secret with the name `test-manage-d--es` with the content from `test-manage-db--es`
- Make sure **manage** CR is using the new secrete under `settings.db.encryptionSecret` in the yml file