nrftool box 2.4.0 Fails to do Single bank bootloader

I am using nrf51822 with softdevice 7.3 and sdk6. I am having some strange problems in single bank bootloader. The nrftoolbox version 2.4.0 gets stuck at 94% during the firmware update. But it works fine with nrftoolbox version 1.16.5. What could be the problem? Why does it fails in latest version?