Partial error with custom external loader

Hello,

i created my own external loader for STM32F767IGT MCU with W25Q256 QuadSPI FLASH.

When i read its memory with STM32CubeIDE i can see all of it and the test works perfectly. But when i read it with STM32 Programmer i see only 99999999 until about 0x90000400.

I can write to it but 99999999 still remains.