While ota dfu via nrf toolbox android app, it sends wrong (0x15918) image size in start packet, and also bootloader starts writing softdevice image at address DFU_BANK_0_REGION_START(0x18000) instead of DFU_BANK_1_REGION_START(0x2A000). But it works fine with Application and bootloader dfu.
nrf chipset is : nRF51822 QFAA
Settings for nrf toolbox application are: packet recipt notification proc... : true Number of packets : 100 MBR size : 4096 Keep bond information : false External MCU DFU : fasle