Hi, I would recommend calling phone support, it should be possible to reflash ONIE and the OS from the diag OS loading the files through USB, but not all of the commands are public so I can’t post them here.
Hi, After a firmware update, the switch is no longer able to boot. 10.4.3.6 -> 10.5.2.2 On boot, it stuck on grub rescure and it is not able to load ONIE Boot Menu or OS10. I'm able to access to DIAG-OS, is possible to repair grub/ONIE/OS from external USB ? Thanks  
S5248F-ON stuck on grub