STM32H7 Firmware Memory Fix

I have a very simple STM32H7 firmware that write and read to large array in RAM. I am running into what looks like memory management issues, even if I am way under the available RAM. I need someone experience with memory management on STM32 to find the issue and fix it. I expect this to be a very quick job (less than an hour) for somebody familiar, so I would need it done quickly (within 1-2 day) and at a low price (1-2 hours at your hourly rate). You don't need to own the hardware as I can test on my side. This is just the first small task on this big project, so it will lead to many more jobs if you are successful. More details are in the attached document, so please read it carefully.