Posting multi-part form data to HP Trim from power automate giving error with status 400

Hi 
I am trying to post a file to HP Trim content manager using Power automate cloud flow. 
I am using on-premise connection gate way to connect to the service api on our network.
 
I can post a record using json (without the file) from the flow and it works fine.
 
When I post a Multi-part form-data along with the file content I get Status 400 and object missing exception, which is kind of generic error as service api is not able to recognize(decipher) the data I am passing. 
 
I am able to post the same data from Postman and it works fine. 
 
I can do the same using http client in .NET C# code and it works fine. 
 
I even tried to the post the data from Postman and got the request in power flow using the "When a request a received" action.
Used this request to post to HP trim but so far unsuccessful. 
 
I have spent many days trying to get it work. 
 
I would appreciate any help from the forum contributors and users. 
 
Thanks a lot in advance, Nalina
 
here is the power flow screen