scriptrunner create subtask and update custom field

[Derek Imrie]

I'm using the scriptrunner post function create sub task template.

The subtask is being created as expected but i'm trying to update a custom field when the task is created.  When i use some code that i found on the Adaptavist website i get an error

https://library.adaptavist.com/entity/update-the-value-of-custom-fields-through-the-script-console 

this is the code in the script context window

def response = put("/rest/api/2/issue/${issue.key}")
.header("Content-Type","application/json")
.body([
fields:[
customfield10076: 'Change Exception Approver'
]
])

.asString()

Error 

2020-01-07 14:58:13.679 WARN - PUT request to /rest/api/2/issue/RFC-7031 returned an error code: status: 400 - Bad Request
body: {"errorMessages":[],"errors":{"customfield10076":"Field 'customfield10076' cannot be set. It is not on the appropriate screen, or unknown."}}
2020-01-07 14:58:13.925 INFO - PUT /rest/api/2/issue/RFC-7031 asString Request Duration: 3200ms
2020-01-07 14:58:15.548 INFO - Serializing object into 'interface java.util.Map'
2020-01-07 14:58:15.549 INFO - POST /rest/api/2/issue asObject Request Duration: 1590ms
2020-01-07 14:58:15.559 INFO - Created subtask completed

 customfieldid10076 is the custom field that i'm trying to update.  I've confirmed that it is on the screen for the sub-task.  The custom field is a single group picker.

If i use the same code and try to update the description it works fine so the issue is definitely to do with the customfield. 

Any help appreciated  

[David_Bakkers]

You seem to have the wrong syntax for identifying the field. The format is 'customfield_nnnnn' not 'customfieldnnnnn'.

[Derek Imrie]

Hi, I've updated the script but still get the same error

2020-01-09 08:56:32.714 WARN - PUT request to /rest/api/2/issue/RFC-7123 returned an error code: status: 400 - Bad Request
body: {"errorMessages":[],"errors":{"customfield_10076":"Field 'customfield_10076' cannot be set. It is not on the appropriate screen, or unknown."}}
2020-01-09 08:56:32.734 INFO - PUT /rest/api/2/issue/RFC-7123 asString Request Duration: 599ms
2020-01-09 08:56:33.556 INFO - Serializing object into 'interface java.util.Map'
2020-01-09 08:56:33.558 INFO - POST /rest/api/2/issue asObject Request Duration: 783ms
2020-01-09 08:56:33.559 INFO - Created subtask completed