Getting errorcode 151 invalid Json on API - Update execution for Jira Zephyr test case

[Jiraintegration]

Hi,

I am getting following response as error on hitting Update execution status API with URL -:

https://prod-api.zephyr4jiracloud.com/connect/public/rest/api/1.0/executions/20c53535-71dd-42ad-af07-8a05e994667a/customField

"errorType": "ERROR",    "clientMessage": "Invalid Json",    "errorCode": 151

I am first trying to hit the API manually and gave JWT key in authorization, zapiAccess key and Content Type.
Please help to let me know what I am doing wrong

Here is my screenshot for the error in postman tool with response

[Lukas Pollak]

i have same problem - Invalid JSON

[jagadeesh madhura]

Please recheck the payload, looks like there is error in your input

Sample request and response you can refer at 

https://zfjcloud.docs.apiary.io/#reference