Vault pods stuck in sealed state

[rashiga]

We have deployed a vault cluster in HA mode with Etcd as a backend storage. It was deployed and started running seamlessly but suddenly the vault pods got into sealed state and were not getting unsealed when we tried it manually.
The error we were getting was :
Error unsealing: Error making API request.

URL: PUT https://127.0.0.1:8200/v1/sys/unseal
Code: 500. Errors:

• failed to decrypt encrypted stored keys: cipher: message authentication failed

The Etcd backend was running fine with no errors but the vault pods went down.