I found the issue, and I want to share the solution for future visitors to this thread.

The problem was caused by the use of the annotation:

@ResponseStatus(HttpStatus.ACCEPTED)

This annotation was redundant in my case. It likely caused the connection to be closed prematurely, preventing the application from functioning correctly.

Solution:

After removing the @ResponseStatus(HttpStatus.ACCEPTED), the application started working as expected. If you're facing a similar issue, consider whether this annotation is necessary for your use case, as it might interfere with response handling.