nrf5340 how to forcefully enter into DFU mode if a buggy APP is loaded via DFU ?

How can we forcefully enter into DFU mode in NRF5340 if for example the newly loaded application due to a bug is unable to advertise BLE?
In another words, if I press reset button, I want the device to be in DFU mode for at least 10 seconds so that I can recover the  device in case if the application crashes.

At present the DFU bootloader is a standalone bootloader with BLE capability or is jt just a switcher which jumps to the application downloaded new image partition?