I apologize for the confusion. It seems the issue persists. To further diagnose the problem, it's important to understand that this code involves a lot of low-level operations, including the use of `clone` and setjmp/longjmp. This can introduce complexity and potential issues.

To better assist you, I would recommend simplifying the code and possibly considering a different approach, or using higher-level threading libraries like pthreads in C. This will provide a more stable and reliable threading environment.

If you're committed to using this custom threading implementation, I would suggest carefully reviewing the logic for any potential race conditions or pointer errors. Debugging low-level concurrency issues can be challenging and may require a thorough analysis of the code flow.