ETag not working as expected and getting an error "RESOURCE_MODIFIED"

Please help us ASAP, tried as below:

Scenario 1

We are passing Etag Parameter through "PUT" Request for "agreement/{agreementid}/formfields" that we get from GET Request "agreement/{agreementid}" headers key "ETag"

We tried as per given in the documentation: 

https://www.adobe.io/apis/documentcloud/sign/docs.html#!adobedocs/adobe-sign/master/api_usage/enhancements_v6.md#etag-support

Bur still getting the error as below:

{
     "code": "RESOURCE_MODIFIED",
     "message": "Resource is already modified with newer version"
}

Scenario 2

We also tried creating new GUID for every GET Request "agreement/{agreementid}" and sending as  parameter for "if-none-match" = GUID. Then doing "PUT" Request for "agreement/{agreementid}/formfields" by passing "Etag" Parameter with the same "GUID" that was created above. Still getting the same error: 

{
     "code": "RESOURCE_MODIFIED",
     "message": "Resource is already modified with newer version"
}

Enviroment being used:

1) .NET Framework 4.6.1

2) Adobe Sign REST API Version 6 Methods.

3) AdobeSignCSharpSDK from Github