Jira Software error PUT API "no single-String constructor/factory method"

[Tejas Srikantappa]

I get the below error message when I update the custom field from API. not sure what i am doing wrong, please help!

Error : 
{'errorMessages': ['Can not instantiate value of type [simple type, class com.atlassian.jira.rest.v2.issue.IssueUpdateBean] from JSON String; no single-String constructor/factory method']}

Data that i am sending:

{
    "update": {
        "customfield_25305": [ {"set": [{"value": "c6f1e31ce0138cba658f769accaac729bebc42d6" } ]} ]
    }
}

[Tejas Srikantappa · Accepted solution]

I was able to resolve the issue, the proper formatting for data is as below:

{"fields": {"customfield_25305": "\"1c1a07d49af1b1cde8a1a7bd93cbbeef8efd50c9\", \"c6f1e31ce0138cba658f769accaac729bebc42d6\", \"1c1a07d49af1b1cde8a1a7bd93cbbeef8efd50c9\""}}

[Prince Nyeche]

What type of field (field type) are you trying to update? Depending on the field type, there are specific ways the update should occur. 

[Tejas Srikantappa]

Thanks for responding @Prince Nyeche , the field type would be string i believe.
when i made get call as per documentation using "/editmeta" i got below.

{'required': False, 'schema': {'type': 'string', 'custom': 'com.atlassian.jira.plugin.system.customfieldtypes:textfield', 'customId': 25305}, 'name': 'Commit ID(s)', 'fieldId': 'customfield_25305', 'operations': ['set']}