Error parse JSON body your request

good morning everybody. I’m having an error when I use the api with the gpt-4 model. I pass the prompt and context parameters, it turns out that when I send the conversation history in the context parameter, I receive a JSON error (attachment). I have already cleaned the text of special characters, transformed the text into UTF-8, but the error persists. The strangest thing is that when I run the api with simple texts it doesn’t give an error. my application is in flutter, the input is a string, the variables used are in string. Would anyone have any suggestions to resolve this problem? Thank you in advance. Helvio