V91 Error updating global configuration in the API Server

Hi,

In v91, all of a sudden, I'm getting this strange error everytime I want to apply global changes to any of the apiserver web applications, such as portal for instance. 

2023-10-03 13:23:03.8122 ERROR (    WebLog ) : An error occurred while processing the request: POST xxxxxxxx/.../portal System.Exception: An error occurred while processing the request: POST iam-sserver3.eprinsa.org/.../portal ---> Newtonsoft.Json.JsonSerializationException: Type specified in JSON 'System.Object[], mscorlib' was not resolved. Path 'Scopes[1].Data['ServerConfig/PersonConfig/VI_Employee_MasterData_Attributes'].$type', line 1, position 580.

It works fine if I apply them locally. I guess something got corrupted somewhere but I cannot find where to fix it.

It is always the same error , for the same key VI_Employee_MasterData_Attributes. I know I've changed values for this key earlier this morning, but it was working alright afterwards. Then, suddenly, no matter which key in the apiserver config I want to modify globally , the error appears in the web page and that error above gets logged in the server log. I cannot even revert the configuration to default. Even that action triggers the error. I've installed another apiserver in a different machine to the same result.  I'm desperate.