Modifying the question and forcing the survey to be answered
Currently, the Csat question is "How did the chat go?", for "Do you consider your problem was solved?", having more focus on the agent's resolution and not on whether the chat worked.
Or put more than 2 options in examples of questions to choose from without being personalized.
Also put an option that forces the user to answer the survey, e.g. do not allow to open another chat until they check answer the evaluation and if they mark it as not resolved, open again the same ticket.