An NFX250 device tries to boot up (either from a reboot or a hard boot), but it hangs after the "starting udev" message. This article indicates what must be done when this situation is encountered.

The NFX250 device seems to be booting properly, but it stalls. The following is a sample from the console, while the device attempts to boot up:

Booting `Juniper Linux'

Loading Linux ...
error: no suitable video mode found.
Booting in blind mode
i8042: No controller found
First Level Bootstrap using initramfs...
Mounting boot device LABEL=LINUX-BOOT
Unpacking initrd.cpio.gz ....
1528137 blocks
Unmount boot device LABEL=LINUX-BOOT
INIT: version 2.88 booMouting VAR to /var
Starting udev

Based on the symptoms, the Linux OS seems to be attempting to access some component on the device (most likely the SSD), and it is failing. This could happen due to file system corruption on the SSD.

Recovery can be done by either doing a USB install or simply RMA'ing the device, and implementing a hardware replacement.