Updating an insight field via REST API

[Koczka Bence]

I want to change some Object Attributes in an Object Schema. 

I set up a test schema with the default object attributes, plus one text field, which I'd like to change.

Based on the documentation (https://documentation.mindville.com/display/ICV50/Objects+-+REST) I need to make a PUT request to /rest/insight/1.0/object/{id}, which I do with a body of

{    
"objectTypeId": 689,    
"attributes": [{        
"objectTypeAttributeId": 2727,        
"objectAttributeValues": [{            
"value": "plshelp"        
}]    
}]}

The response status is 200 OK, but It does not affect any changes on the Insight field. The response is exactly the same, as the one I receive when I try to Get an item (/rest/insight/1.0/object/{id}, same exact address, with GET request type). 

Also I noticed, that no matter what I write in the body, the response stays the same, seems like the API does not process it at all. 

The response, if needed(https://pastebin.com/1zh5CCkj)

Any ideas what I am missing here?