Erase/Flash with buit-in bootloader on BlueNRG-2 via UART

[H W]

I have problems to write to flash memory at address 0x10040000 via UART bootloader on BlueNRG-2.
Flash start is 0x10040000, but I can only flash the memory from 0x10042000 on, which is a 8kB offset !?

The memory is successfully erased before.

Second question: when I erase the pages I can only go up to page 124 (0..123). Pages 125..128 are NACKed !?

Can anyone clearify this?
Regards.