Error in Import survey API from MS Power Automate (Flow)

Hi Folks,
I am fairly new to Qualtrics but an experienced programmer. I am trying to create a new survey using import survey APIs (using TXT file as input for questions and options) from a Microsoft Power Automate (now called as Flow) process. I am using HTTP action in Power Automate and after trying multiple times with request body, I am getting this error from the API
 "httpStatus": "400 - Bad Request",
    "error": {
      "errorMessage": "Unexpected end of input"
    }
I am not doing anything fancy in the import file. Its a simple import file. Just adding name of the survey and file in the multipart/form request.
I tried the API with same txt file in postman and it works. I think there is something fishy with Power Automate and how it makes that call but not getting any insights from the API response to figure out what is wrong. Any help is highly appreciated.