I was able to replicate your error and pushed a fix, it should be working pretty reliably now for equations that include theta. Let me know if it works for you!
Thanks for the feedback. We can improve the model's focus on the task at hand and/or ask for more details if doesn't have enough context. With a bit more clarification, MathGPT outputs your answer: https://math-gpt.org/?problem_text=solve%20x%20mod%2066%20%3....
