I was able to reproduce the issues you reported. I will ask someone relevant to work on it.
Anyways I would just like to point out that the above kernels are having serious multiple work-items writing to same location bug. I understand, this kernel might only be for showcasing the codexl bug, but just be careful in case you are using the above kernel and wondering about correctness failures.
I would recommend to post similar issues in the codexl section.