XG lost configuration while uploading firmware v18-MR5

Hello Community,

I've uploaded the Firmware v18-MR5 to several XG Firewalls (~30, mixed SG/XG 115 up to 525). Two XG125 "died" while uploading the firmware (installed Firmware is v18-MR4). It means the firewalls has lost their configuration. The boxes are not reachable with the configurated IP address nor with the default IP ( These firewalls are located in far away offices so I can’t investigate to issue.
We restored the Firmware v18-MR4 with an USB-Sick and applied the configuration backup. After the boxes are back I was able the Upload the Firmware to this firewalls.