What does "Failed: The algorithm failed on one or more cases" mean?

I submitted a test container to the "Prelim testing phase - Category 2" but received a message saying, "Failed: The algorithm failed on one or more cases." I’m unsure where the problem might be in my code. Could you provide more details about the specific issues?

Following is the error message from your submission:

The output file 'surgical-step-classification.json' is not valid. JSON does not fulfill schema: instance 'uterine_horn' is not of type 'integer'